Donald Trump's improbable victory in the US presidential election provoked global shock and angst on Wednesday over the implications for everything from trade to human rights and climate change.

The bombastic billionaire defeated Hillary Clinton in a result that few predicted, as millions of American voters shrugged off concerns over his temperament, lack of experience, and accusations of sexist and racist behaviour.

Trump's rise has been keenly watched abroad as he campaigned on a platform of trashing trade agreements, questioning alliances, restricting immigration and dismissing climate change.

In often hushed scenes, many attendees at election-watching events around Asia expressed deep misgivings about Trump taking the reins of the world's most powerful nation and economy.

Dianita Sugiyo, 34, a university lecturer in Indonesia -- the world's most populous Muslim country -- said she was concerned by Trump's calls to temporarily ban Muslims from countries with histories of terrorism.

"He has always been anti-Muslim and I am afraid he will discriminate against Muslims," said Sugiyo, a member of a leading Indonesian moderate Muslim organisation.

"The United States is a multicultural country and there are a lot of Muslims there, so this is very terrifying," she added, speaking at a US embassy event in Jakarta.

The election of an opponent of free trade caused financial markets across Asia to plunge, with Tokyo's main index tumbling more than 5 percent, while stock futures on US and European markets also fell when they opened.

"The world is globalising and if the US, which is one of the economic powerhouses, is going to put up walls, I don't see that as good for the world economy," said Clarita Carlos, a political science professor at the University of the Philippines.

"They can practically slow down economic growth for everybody. He is a businessman. He should know better."

- 'Dangerous' for the planet -

Trump has vowed to ditch the 12-nation Trans-Pacific Partnership (TPP) trade agreement, perhaps President Barack Obama's main diplomatic legacy in the region.

Tang Siew Mun, head of the ASEAN Studies Centre at the ISEAS-Yusof Ishak Institute in Singapore, said such moves would severely damage the US in a region where China is posing a growing leadership challenge.

"For us in the region, we ask these questions: does America still stand for free trade as far as TPP is concerned? Will America stand for and engage internationally as a global leader?" he said, speaking on Channel NewsAsia.

Environmentalists also recoiled, as Trump has threatened previously to "cancel" the historic UN pact struck last year to address climate change.

"What have we become?" asked Greenpeace Southeast Asia's Executive Director Yeb Sano.

"On climate change, clearly this is a massive blow to our prospects of progress and hope that the Paris Agreement had given us."

At election events around the region, American Democratic supporters gradually deflated as Trump's victory materialised, while Republicans were buoyed.

Bradley Jordan, a retired 59-year-old Californian in Bangkok, said a Trump win would "throw the whole world upside down."

"It's dangerous for the planet. If Trump wins, we will do nothing about climate change and the planet will be screwed. I just can't believe this is happening right now," he said, adding he was contemplating renouncing his US citizenship.

Even some Republicans expressed surprise at Trump's win.

"To be honest we didn't really think he would win," Kym Kettler-Paddock, a US Republican, said at an election event in Hong Kong.

She said the panic over Trump would subside as he makes it known what sort of leader he would be.

"I think after that transition period (the uncertainty) would settle down," she said.

Others, however, pointed to Trump's friendly comments toward the likes of Russian President Vladimir Putin as indicating America may no longer carry the torch for human rights.

"The fact that authoritarian leaders around the region find hope in the possible election of Donald Trump as president is a telling indicator of what they think his policies on human rights will be," said Phil Robertson, deputy Asia director for Human Rights Watch.

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