World

TOKYO/SEOUL — North Korea said on Sunday a push for further sanctions following its fifth and biggest nuclear test was "laughable", and vowed to continue to strengthen its nuclear power.

The isolated state on Friday set off its most powerful nuclear explosion to date, saying it had mastered the ability to mount a warhead on a ballistic missile, ratcheting up a threat that its rivals and the United Nations have been powerless to contain.

A US special envoy met with Japanese officials on Sunday and said later the United States may launch unilateral sanctions against North Korea, echoing comments by US President Barack Obama on Friday in the wake of the test.

"The group of Obama's running around and talking about meaningless sanctions until today is highly laughable, when their 'strategic patience' policy is completely worn out and they are close to packing up to move out," state-run KCNA news agency cited a North Korean foreign ministry spokesman as saying in a statement later on Sunday.

"As we've made clear, measures to strengthen the national nuclear power in quality and quantity will continue to protect our dignity and right to live from augmented threats of nuclear war from the United States," KCNA added.

Earlier, the South's Yonhap news agency reported South Korea's military had a plan to use its missiles to "decimate" areas of Pyongyang if there were signs the North was about to launch a nuclear attack, quoting a source in the military.

The South's defence ministry could not immediately confirm the report, but the military has vowed to take strong actions to retaliate in the event of an attack by the North.

The North has yet to demonstrate that it had deployed nuclear-capable missiles, despite claims to have mastered the technology to miniaturise a nuclear warhead to mount it on ballistic missiles.

The UN Security Council denounced North Korea's decision to carry out the test and said it would begin work immediately on a resolution. The United States, Britain and France pushed for the 15-member body to impose new sanctions.

Obama said after speaking by telephone with South Korean President Park Geun-hye and with Japanese Prime Minister Shinzo Abe on Friday that they had agreed to work with the Security Council and other powers to vigorously enforce existing measures and to take "additional significant steps, including new sanctions".

"We will be working very closely in the Security Council and beyond to come up with the strongest possible measure against North Korea's latest actions," said US envoy Sung Kim on Sunday.

"In addition to action in the Security Council, both the US and Japan, together with the Republic of Korea, will be looking at unilateral measures, as well as bilateral measures, as well as possible trilateral cooperation," he said, referring to South Korea by its official name.

South Korea's top nuclear envoy also spoke to his Chinese counterpart late on Saturday by telephone and emphasized the need for fresh countermeasures including a new UN security council resolution during their call, the South Korean foreign ministry said in a statement.

South Korea said on Saturday that the latest test showed North Korea's nuclear capability was expanding fast and that North Korean leader Kim Jong-un was unwilling to alter course.

Another KCNA report on Sunday said North Koreans were "delighted" by the nuclear test.

"The enemies can no longer deny the strategic position of our country as a nuclear weapons state," Jong Won-sop, a teacher at the University of National Economy, was quoted as saying. 

SEOUL — North Korea on Saturday sought to justify its weapons programme as a defence against US nuclear "blackmail" as world powers debated ways to punish Pyongyang for its fifth and most powerful atomic test.

South Korea said the nuclear threat from its wayward neighbour was growing fast and called for tough new sanctions from the UN Security Council to force it to change tack.

The yield from Friday's test, which sparked international shockwaves, was estimated at 10 kilotonnes — almost twice as much as the one Pyongyang conducted only eight months ago.

The North also boasted that the test was of a nuclear warhead that could be mounted on a missile. 

"It is believed that the North's nuclear capability is becoming more advanced to a considerable level, and at a faster pace," Foreign Minister Yun Byung-se told senior ministry officials, calling for "more and stronger sanctions".

The UN Security Council agreed to start work on just that — even though five sets of UN sanctions since the first nuclear test a decade ago have failed to halt the North's drive for what it insists are defensive weapons.

During a closed-door meeting on Friday, the council strongly condemned the test and agreed to begin drafting a new resolution under Article 41 of the UN charter, which provides for sanctions.

"The members of the Security Council will begin to work immediately on appropriate measures under Article 41 in a Security Council resolution," New Zealand's Ambassador Gerard van Bohemen, who holds the council's rotating presidency, told reporters.

South Korea, the United States, Japan, Russia and China all condemned the blast at the Punggye-ri nuclear site.

In Seoul, dozens of protesters burned an effigy of the North's leader Kim Jong-un and called for "strong retaliation", including pre-emptive attacks on the North's nuclear complex.

"Eliminate Kim Jong-un!" and "Destroy North Korea's nuclear weapons!" the elderly activists shouted.

Some newspapers were equally scathing. "South Korea left unguarded before nuclear maniac," read the banner headline of the top-selling Chosun Ilbo.

But the North's ruling party newspaper vowed on Saturday not to submit to US nuclear "blackmail", and described the South's President Park Geun-hye as a "dirty prostitute" for working with US forces.

"Gone are the days never to return when the US could make a unilateral nuclear blackmail against the DPRK," said Rodong Sinmun, using the country's official name.

"The US is exasperated by the strong military steps being taken by the DPRK in a phased way."

'Holding the world hostage' 

The US stations 28,500 troops in the South. The Joongang Ilbo newspaper recommended they should be armed with tactical nuclear weapons, as they were until the early 1990s.

The Security Council met at the request of Japan, South Korea and the United States to agree on a response, despite resistance from Pyongyang's sole ally China to calls for tougher measures.

After Pyongyang carried out its fourth nuclear test, the council in March adopted the toughest sanctions resolution to date, targeting North Korea's trade in minerals and tightening banking restrictions.

But since that measure was adopted, North Korea has carried out 21 ballistic missile launches, US Ambassador Samantha Power said.

"North Korea is seeking to perfect its nuclear weapons and their delivery vehicles so they can hold the region and the world hostage under threat of nuclear strike," Power said.

Pyongyang's state media said on Friday the nuclear test had realised the goal of being able to fit a miniaturised warhead on a rocket.

"Our nuclear scientists staged a nuclear explosion test on a newly developed nuclear warhead at the country's northern nuclear test site," a TV presenter said.

North Koreans gathered around public screens to watch the official announcement of the test.

The nuclear programme has accompanied a series of ballistic missile launches, the latest of which took place on Monday as world powers gathered for a G-20 meeting in China.

Challenge for China 

China has long been under pressure to rein in its increasingly aggressive neighbour.

Beijing strongly condemned the test. But its priority is to avoid the regime's collapse, which would create a crisis on its border and potentially shift the balance of power on the Korean peninsula toward the United States.

US Defence Secretary Ashton Carter called for further pressure on North Korea, but said China bore responsibility for tackling the problem.

"China shares important responsibility for this development and has an important responsibility to reverse it," he said.

"It's important that it use its location, its history and its influence to further the denuclearisation of the Korean peninsula and not the direction things have been going." 

DHAKA — A fire at a food and cigarette packaging factory in Bangladesh killed at least 23 people and injured dozens on Saturday, in the country's worst industrial accident since the Rana Plaza building collapse of 2013 in which over 1,100 people died.

Emergency officials feared the death toll could climb after a fire broke out in the Tongi industrial zone about 20km north of the capital, Dhaka.

The cause was not immediately known, but officials said a boiler explosion probably triggered the blaze at around 8am (0200 GMT) as workers prepared to swap shifts.

"There were about 100 people inside the building when fire broke out," Mohammad Nayan, a worker who was helping with rescue efforts, told reporters.

Officials at the site said over 20 firefighting teams were working to quell the blaze at the Tampaco Foils plant, which caused the partial collapse of the factory building.

"We cannot confirm whether any people are inside or not, but our priority is to rescue them if there is anyone inside," Mohammad Akhtaruzzaman, a fire department official at the site, told Reuters over the phone.

Another fire official said that although the blaze was under control, there were still flames inside the building so firefighters had been unable to search the debris.

A manager at Tampaco Foils said he did not know how many people were inside the factory when the blaze broke out.

"Now my only focus is on my workers who were injured and on those who died. We will take care of them," said Syed Mokbul Hossain, chair of Tampaco and a former member of parliament.

"My company is fully compliant and I've never sacrificed on quality, as my clients are mainly multinational companies."

Tampaco's website says its clients include several local companies and global brands including British American Tobacco and Nestle.

Fire department officials initially identified the factory as a garment packaging plant, but later clarified that it packs food and cigarettes.

The fire will further tarnish the industrial safety record of one of the world's top garment exporters.

In the Rana Plaza disaster, 1,135 mainly garment industry workers were killed when a building collapsed outside Dhaka.

That sparked demands for greater safety in the country and put the onus on multinational companies sourcing clothing from Bangladesh to act.

The disaster led to the creation of two international coalitions designed to help fund improvements to building and fire safety at thousands of garment factories across Bangladesh.

The latest incident comes weeks after over 100 people fell ill when they inhaled gas that leaked from a fertiliser plant in the town of Chittagong in southern Bangladesh. 

WHITE PLAINS, New York — US Democratic presidential candidate Hillary Clinton chastised Republican rival Donald Trump on Thursday for talking about things he learned in classified intelligence briefings, calling it "totally inappropriate and undisciplined”.

Speaking to reporters the morning after a New York security forum featuring separate appearances by the two candidates, Clinton also slammed the businessman for praising Russian President Vladimir Putin and saying US generals had been "reduced to rubble" by the policies of US President Barack Obama.

At the televised forum on Wednesday night, Trump said he was "shocked" by information he got during the briefing. "What I did learn is that our leadership, Barack Obama, did not follow what our experts ... said to do," Trump said.

"I would never comment on any aspect of an intelligence briefing I received," Clinton, a former secretary of state, said before boarding her campaign plane. As nominees for the November 8 presidential election, she and Trump are entitled to receive intelligence briefings.

Clinton said Trump's praise of Putin as a better leader than Obama was "not just unpatriotic" but also “scary”.

"It suggests he will let Putin do whatever Putin wants to do and then make excuses for him," Clinton said.

Trump's campaign fired back at Clinton after her session with reporters, saying she was resorting to "unhinged and dishonest" attacks.

"These are the desperate attacks of a flailing campaign sinking in the polls, and characteristics of someone woefully unfit for the presidency of the United States," Jason Miller, senior communications adviser for Trump, said in a statement.

Clinton's lead over Trump in national opinion polls has weakened in recent days. The current average of polls by website RealClearPolitics puts her at 45.6 per cent support, compared to Trump's 42.8 per cent.

Obama also hit back at Trump for criticising his foreign policy record, saying the Republican nominee was unfit to follow him into the Oval Office and the public should press him on his "outright wacky ideas”.

The televised "Commander-in-Chief" forum on Wednesday, attended by military veterans, was the first time Trump and Clinton had squared off on the same stage since accepting their parties' White House nominations in July, although they did not appear at the same time.

It offered a prelude to how Clinton and Trump will deal with questions of national security in their three upcoming presidential debates later in September and in October.

Clinton has said her experience in government as secretary of state and a US senator makes her uniquely qualified for the White House, and that Trump's series of controversial comments makes him temperamentally unfit for the office.

Some of Trump's foreign policy positions, such as his proposal to fight terrorism by imposing a temporary ban on Muslims entering the country, have alarmed not just Democrats but many in his own party's leadership.

Trump, who has never held elected office, has criticised Clinton's judgement, attacking her vote in favour of the 2003 Iraq war and her support for the US intervention in Libya in 2011. The Republican candidate was widely criticised recently when he called her a "co-founder", along with Obama, of Daesh.

Clinton said on Thursday she would convene a meeting of bipartisan security experts on Friday to discuss the fight against Daesh militants.

"What you didn't hear from Donald Trump last night was any plan to take on ISIS," Clinton told reporters, using an acronym for the Daesh group. "That's not only dangerous, it should be disqualifying."

Trump and Clinton supporters went on the offensive on social media Wednesday night and Thursday morning, defending their candidates' performances during the forum.

Trump campaign manager Kellyanne Conway met with Trump supporters in Congress on Thursday morning, and Trump spoke with the group by phone to thank them for their support. Afterwards, some of his supporters shrugged off his comments about Putin.

"I think he is being very smart in how he addresses Putin and you know, maybe he's playing with Putin's ego," said Representative Marsha Blackburn of Tennessee.

Clinton said Republicans holding or seeking office across the country should be pressed on whether they agree with Trump's comments, including his views on Putin and US generals that surfaced during the forum.

VIENTIANE — Outgoing President Barack Obama condemned Donald Trump as unsuitable to be commander-in-chief Thursday, after the Republican nominee blasted US military brass and praised Vladimir Putin.

"I don't think the guy's qualified to be president of the United States, and every time he speaks, that opinion is confirmed," Obama said in unusually caustic language while overseas.

Obama, who was in Laos for a summit with Southeast Asia leaders and his final trip to east Asia, said that Trump holds contradictory and "outright wacky ideas" and is "uninformed".

"I can tell you from the interactions I have had over the last eight or nine days with foreign leaders that this is serious business," Obama added.

"You actually have to know what you are talking about and you actually have to have done your homework. When you speak, it should actually reflect thought out policy you can implement."

Trump on Wednesday raised eyebrows by saying that Russia's president was "far more" of a leader than Obama.

Putin is "very much of a leader", Trump said in a televised interview.

"It's a very different system, and I don't happen to like the system. But certainly in that system he's been a leader, far more than our president has been a leader."

Trump also drew fire for criticising the military.

"The generals have been reduced to rubble," Trump said, before noting he had "faith in certain of the commanders".

The bombastic mogul will face Hillary Clinton in November's election, which the Democratic former first lady is tipped to win.

Trump has previously angered many in the military community with mocking remarks against US Senator and former prisoner of war John McCain for being captured in Vietnam.

Speaking in Laos about Trump's unsuitability for office, Obama observed that over the course of the election season "people start thinking behaviour that in normal times we would consider completely unacceptable and outrageous becomes normalised".

Obama is expected to hit the campaign trail with Clinton when he returns to the United States, with voter turnout likely to be a key theme.

Obama won the 2008 and 2012 presidential elections handily by mustering large numbers of young, black, Latino and Asian voters to go to the polls.

ALMATY, Kazakhstan — Uzbekistan's parliament approved Prime Minister Shavkat Mirziyoyev as acting president on Thursday, a government website reported, in the clearest sign yet he could take over long term after the death of veteran strongman Islam Karimov.

Mirziyoyev, 58, was given the post after being backed by senate leader Nigmatilla Yuldashev, who under the constitution should have become temporary president ahead of elections. 

Parliament also ordered a presidential vote to take place within three months with many analysts expecting Mirziyoyev to win.

Mirziyoyev has been widely tipped by analysts to succeed autocrat Karimov.

The 78-year-old president was buried on Saturday in his native Samarkand city, of which Mirziyoyev was a former governor.

Mirziyoyev has had meetings with both Russian President Vladimir Putin who laid flowers at Karimov's grave on Tuesday, and Prime Minister Dmitry Medvedev, who attended the funeral. 

Putin praised Karimov for maintaining "stability" over the course of his 27-year rule and said Russia would "do everything to support the Uzbek people and the Uzbek leadership".

"You can count on us fully, as you can on your most faithful friends," Putin told Mirziyoyev when the two met on Tuesday.

Uzbekistan, a Central Asian country of over 30 million people, has one of the world's poorest records on human rights but has parlayed its strategic location on the border with Afghanistan into geopolitical influence.

The United States once maintained a military base there used for Afghanistan operations, but the government cancelled the lease after Washington called for an independent investigation into a brutal crackdown in 2005.

The country is rich in cotton, gold, gas and other commodities, but close to two million Uzbeks work abroad in Russia, rather than at home, where unofficially unemployment is high. 

It remains an extremely tightly controlled state — the largest in the Central Asian region — so few can be sure what a new leader will mean for the country.

But analysts are certain that key elements of the authoritarian system crafted by Karimov will survive his death. 

"[Mirziyoyev] was known as a guy who would not ask questions but just get things done," Bakhtiyor Nishanov, deputy director of Eurasia for the International Republican Institute, a Washington DC-based pro-democracy nonprofit told AFP by telephone.

One other contender also viewed as potential successor to Karimov is Deputy Prime Minister Rustam Azimov, who appeared alongside Mirziyoyev at the funeral despite some media reporting his arrest. 

Karimov's elder daughter Gulnara Karimova, 44, was also once considered a potential successor, but has since fallen foul of the elite and her own family and is believed to be under house arrest. 

BRUSSELS — A Moroccan man wielding a knife attacked two Belgian police officers in the capital Brussels on Wednesday but their body armour protected them and they were not seriously hurt, prosecutors said.

Prosecutors said other officers arrested the 24-year-old man just after the attack in the Molenbeek district where several men linked to last year's Daesh-claimed attacks in Paris lived.

The Brussels prosecutor's spokesman Ine Van Wymersch told AFP that the man had been staying illegally in Belgium and ordered several times to leave the country.

But he added that the assailant had said nothing during the incident that could suggest a terrorist motive, adding he has in the past been linked to thefts and shoplifting but not terrorism.

He said the man attacked the police officers when they approached him in response to an appeal from a woman who had reported man with a knife in Bonnevie Park.

"One of the officers received seven knife blows and the other received one, but they were protected by their bullet-proof vest and were not wounded," Van Wymersch said.

However, RTL television showed one of the officers, a woman, covered with a small bandage over her right arm.

In August, a Belgian policewoman shot and killed a machete-wielding Algerian man who wounded two female colleagues in the city of Charleroi, south of Brussels.

Daesh claimed responsibility for that attack by a man officials said had been living illegally in Belgium.

Belgium has remained on high alert following deadly extremist bombings in March that killed 32 people at Brussels airport and on the city metro which were also claimed by Daesh.

VIENTIANE — Beijing came under pressure at an Asian summit Wednesday over its "illegal" island building in the South China Sea, after the Philippines produced photos it said showed fresh construction activity at a flashpoint shoal.

Any artificial island at Scarborough Shoal could be a game-changer in China's quest to control the South China Sea and raises the risk of armed confrontation with the United States, security analysts say.

Beijing insists it has not started building at the shoal — a move that could lead to a military outpost just 230 kilometres from the main Philippine island, where US forces are stationed.

But the Philippines released images which it said showed Chinese ships in the area that were capable of dredging sand and other activities required to build an artificial island.

The photos were released during an annual summit of the 10-member Association of Southeast Asian Nations (ASEAN) in Laos, and the bloc voiced alarm.

"We remain seriously concerned over recent and ongoing developments and took note of the concerns expressed by some leaders on the land reclamations," said a joint statement at the end of their two-day summit.

China claims nearly all of the South China Sea, through which $5 trillion in trade passes annually, even waters approaching the coasts of the Philippines and other Southeast Asian nations.

The competing territorial claims have long been a major source of tension in the region, with China using deadly force twice to seize control of islands from Vietnam.

Illegal island building 

Tensions have escalated sharply in recent years as China built islands and airstrips on reefs and islets in the Spratlys archipelago — another strategically important location — that are capable of supporting military operations.

The United States has reacted to that build-up by sailing warships close to the new islands, and sending warplanes over them, deeply angering China.

A UN-backed tribunal ruled in July that China's claims to most of the sea had no legal basis and that its construction of artificial islands in the disputed waters was illegal.

But Beijing vowed to ignore the ruling.

China took control of Scarborough Shoal in 2012 after a standoff with the Philippine navy, and has since deployed large fishing fleets while blocking Filipino fishermen.

Expanding that presence with a military outpost is vital to achieving China's ambitions of controlling the sea, according to security analysts.

US officials fear any Chinese military airfield at the shoal would enable Beijing to enforce a threatened air defence identification zone in the sea.

An outpost at the shoal would also put Chinese fighter jets and missiles within easy striking distance of US forces stationed in the Philippines.

US President Barack Obama reportedly directly warned his Chinese counterpart Xi Jinping during a meeting in March not to push ahead with any island-building there.

Conflict risk

The United States, which is a treaty ally of the Philippines, has repeatedly said it does not want to fight a war over the shoal.

But military skirmishes cannot be ruled out if China does start to build an island, according to security analysts.

"We could witness a physical confrontation between Chinese Coast Guard and Filipino vessels backed up by the US navy," Carl Thayer, an emeritus professor at Australia's University of New South Wales, told AFP.

An Obama aide on Wednesday played down the significance of the Philippine photos, telling reporters the United States had not detected any unusual activity at Scarborough Shoal.

Philippine President Rodrigo Duterte had said he did not want to anger China by highlighting the row at the ASEAN events.

Chinese Premier Li Keqiang, Obama and leaders from other regional powers are also in Laos this week for separate meetings with ASEAN.

But the release of the photos came just a few hours before ASEAN leaders met Li, in what Duterte's spokesman said was a deliberate move.

The ASEAN statement warned that further land reclamation could escalate tensions, and called for respect for United Nations' maritime laws.

Yet the statement did not explicitly call on China to abide by the July ruling, reflecting divisions in ASEAN. 

Cambodian Prime Minister Hun Sen has repeatedly said he does not want to pressure China, his most important ally, over the issue.

Obama had planned to discuss the sea issue during a meeting with Duterte on the sidelines of ASEAN.

But he cancelled after the volatile Philippine president called him a "son of a whore" for expressing concern about Duterte's war on crime which has claimed 3,000 lives.

WASHINGTON — The race between Hillary Clinton and Donald Trump for the White House has tightened with two months to go before Election Day, as a series of new polls Tuesday shows them essentially in a dead heat.

Trump has edged ahead of Clinton in a new CNN/ORC poll, at 45 per cent to 43 per cent among likely voters, while an NBC News poll of registered voters meanwhile shows Clinton's lead holding at six percentage points — 48 per cent to 42 per cent.

And another survey, this one by The Washington Post looking at all 50 states, shows Clinton with a solid lead in terms of electoral college votes, and even strength in some traditional Republican strongholds.

The various polls show how close the race is looking to November 8, and makes the battle for the so-called swing states all the more important.

Clinton was headed to Florida on Tuesday to appear at a voter registration event, while the billionaire real estate mogul was due in Virginia for a town hall meeting and in North Carolina for an evening campaign rally.

"Thank you! #AmericaFirst," Trump tweeted with the new CNN poll results.

The candidates have less than three weeks to go before the first of three scheduled presidential debates — expected to be the most watched moments of what so far has been a raucous campaign.

After hinting last month that he might not participate in all of them, Trump told reporters he was on board.

"I expect to do all three," he said.

'More than ready' 

On Monday, the candidates used Labour Day — the traditional launch of the home stretch of the presidential campaign — to push their arguments that they would be best for working-class Americans.

But the Republican flagbearer's unorthodox White House bid, including his campaign's apparent imperviousness to criticism about his harsh rhetoric, assures a tight contest for the next two months.

"I'm not taking anybody, anywhere for granted," Clinton told a crowd of more than 1,000 at a picnic in Cleveland.

"I'm ready. I'm more than ready," she said of the intense battle ahead as she attempts to become the first female US commander in chief.

Clinton, 68, debuted her new campaign plane — with the slogan "Stronger Together" emblazoned on the side — and brought the press corps aboard her jet for the first time.

Under extensive criticism from her rival and journalists for not holding a full press conference in nine months, she answered questions for more than 22 minutes on several topics, including tensions with Russia over accusations of cyber-espionage.

Clinton expressed "grave" concern about reports that Russia has been interfering in the US electoral process through invasive cyber attacks on the Democratic Party and an apparent attack on voter registration systems in Arizona.

And she implied Moscow was trying to help get the 70-year-old Trump elected.

"I think it's quite intriguing that this activity has happened around the time Trump became the nominee," she said.

Republican messenger 

On Monday, Trump followed Clinton's lead, inviting some journalists aboard his private jet where he discussed his immigration platform.

Just a week after travelling to Mexico for his first international trip as the nominee, and then returning across the US border to deliver a nativist immigration speech, he assailed Clinton for having "no plan" on immigration.

"What her real plan is, she has total amnesty" and a pathway to citizenship, he said, reiterating his opposition to such a legalisation process without undocumented immigrants leaving the country first.

Under Clinton, "people can pour across the border and it doesn't matter who the people are".

Clinton shot back by recalling Trump's meeting with Mexico's President Enrique Pena Nieto and their clash over Trump's plan to have Mexico pay for a border wall.

Trump "can't even go to a friendly foreign country without getting into a fight", she said during a campaign stop in Hampton, Illinois.

Trump, who visited a Cleveland diner to meet with union members and the Canfield County Fair in eastern Ohio, is seeking to capitalise on simmering frustration among blue-collar workers over jobs and wages.

The candidates were joined by their running mates on Monday in Ohio, a signal of the importance each campaign places on the Buckeye State.

Democratic Senator Sherrod Brown of Ohio said there was "more pressure on Trump" than Clinton to win there.

"If Trump loses Ohio, he loses the race," Brown told AFP.

"Hillary can lose Ohio and still win because she's going to win Virginia, North Carolina, Colorado," and other swing states where she has built deep ground operations, Brown added.

VIENTIANE, Laos — Acknowledging the scars of a secret war, President Barack Obama on Tuesday said the United States has a "moral obligation" to help this isolated Southeast Asian nation heal and vowed to reinvigorate relations with a country with rising strategic importance to the US.

Making the first visit by a sitting US President Obama said too few Americans know of the United States' covert bombing of Laos during the Vietnam War. As a first sign of a new relationship, Obama announced he would double spending for unexploded ordnance, committing $90 million over the three years.

Still, he offered no apologies, calling the campaign and its aftermath reminders that "whatever the cause, whatever our intentions, war inflicts a terrible toll".

"Given our history here, I believe that the United States has a moral obligation to help Laos heal," Obama said, as he addressed an audience of more than 1,000 students, businesspeople and officials.

For nine years, the US conducted a punishing, covert bombing campaign on landlocked Laos in an effort to cut off communist forces in neighbouring Vietnam. The bombardment dropped more than 2 million tonnes of ordnance on the small nation, more than "we dropped on Germany and Japan, combined, in all of World War II," Obama said.

The bombing left behind deep scars, millions of unexploded cluster bombs across the countryside and decades-worth of cleanup.

Obama is one of several world leaders arriving for a meeting of the Association of Southeast Asian Nations. Taking its turn as the chair of the regional forum, the Laos' communist government is seizing a rare moment in the spotlight.

For Obama, the visit serves as a capstone to his years-long effort to bolster relations with Southeast Asian countries long overlooked by the United States. The outreach is a core element of Obama's attempt to shift US diplomatic and military resources away from the Middle East and into Asia in order to counter China's dominance in the region and ensure a foothold in growing markets.

Obama's project — dubbed his Asia pivot — has yielded uneven results, as conflict in the Middle East has continued to demand attention and China has bristled at what it views as meddling in its backyard.

Obama said America's interest in the Asia-Pacific is not new and is not a passing fad.

"The United States is more deeply engaged across the Asia-Pacific than we have been in decades," Obama said. "Our positon is stronger and we've sent a clear message that as a Pacific nation, we are here to stay."

With just four months left in office and eying his legacy, Obama used the moment to reassert his aims. He touted new military aid and US support for regional cooperation in addressing maritime disputes. He made a plug for the massive Trans-Pacific Partnership free trade agreement, the policy's central economic component that is now stuck in Congress. He sought to address worries that United States' new focus on Asia will leave smaller nations as pawns in a chess match between the US and China.

"We believe that bigger nations should not dictate to smaller nations and that all nations should play by the same rules," he said.

The $90 million to clean up unexploded bombs joins another $100 million the US has committed to effort in the last 20 years, as annual deaths have fallen from more than 300 to fewer than 50, the White House said.

The Laos government said it would increase efforts to recover remains and account for Americans missing since the Vietnam War.

As he opened a day of ceremony and diplomacy, Obama was greeted by a military band, traditional dancers and a warm, tropical rain. He met with Lao President Bounnhang Vorachit, was feted at a welcome banqueted, where he toasted to a relationship he said would "mean greater progress and opportunity for the people of Laos".

Obama's outreach to those regional powers hit a snag just as he arrived in the region from China. The White House called off a planned meeting Tuesday with Philippine President Rodrigo Duterte, after the brash new leader referred to Obama as a "son of a bitch".

Duterte, who had been expecting Obama to criticise his deadly, extrajudicial crackdown on drug dealers, later said he regretted the personal attack on the president.

In a statement read out Tuesday by his spokesman, Duterte said his "strong comments" to certain questions by a reporter "elicited concern and distress".

"We look forward to ironing out differences arising out of national priorities and perceptions, and working in mutually responsible ways for both countries," the statement said.