[HONG KONG] Share markets collapsed on Wednesday and the dollar tumbled against the yen and the euro as Donald Trump looked on course to win the race for the White House, in a stunning upset with major implications for the world economy.

The Mexican peso also fell to a record low as safe haven assets rallied, with gold soaring more than five percent.

Initial confidence that market favourite former secretary of state Hillary Clinton would win was wiped out as results showed the firebrand tycoon picked up Ohio, North Carolina and Florida - major scalps needed if he is to take the White House.

Markets have been plunged into turmoil as Mrs Clinton is considered by many investors to be a safer bet than Mr Trump, who is seen as a loose cannon with policies many fear could wreck the world's number-one economy.

"It's been a bloodbath in the markets over the last few hours with the Mexican peso suffering particularly badly as Donald Trump edges ever closer to the White House," said Craig Erlam, senior market analyst at Oanda.

Tokyo collapsed 5.5 per cent by the break while Hong fell almost three percent and Shanghai sank 1.3 per cent.

Sydney gave up more than two per cent, Seoul shed three percent and Singapore dived 1.2 per cent. Wellington plunged 3.3 per cent while there were also losses of more than two per cent for Taipei. Jakarta, Manila and Bangkok were all down more than one per cent.

The Sensex on the Bombay Stock Exchange was more than two per cent off having initially plummeted more than six per cent as Mr Trump's impressive performance was mixed with news that high denomination notes were being pulled from circulation as part of a crackdown on tax evasion.

Futures on the S&P 500 and Nasdaq on Wall Street were more than five per cent down while those on the Dow were off four per cent.

"It's quite scary," Nader Naeimi, the Sydney-based head of dynamic markets at AMP Capital Investors, said.

"The slightest move towards Mr Trump moved the market very quickly. The slightest change in the odds is amplifying market moves and this just shows there's a lot at stake."

The Mexican peso - which was battered by Mr Trump's anti-immigrant rhetoric earlier in the campaign - hit a record low against the dollar.

The greenback soared to 20.7135 pesos, around its highest ever point and about 12 per cent up on earlier levels.

The peso has been hammered as Trump's anti-Mexican promises have included a pledge to remove undocumented immigrants, building a border wall and tearing up a trade deal.

However the dollar tumbled against the yen as investors rushed into the Japanese unit, which is considered a safe bet in times of uncertainty and turmoil. The greenback was hovering just above 101 yen, having sat above 105 Tuesday.

The euro also rose 2.1 per cent against the dollar, while gold soared 5.4 per cent to US$1,337.00 an ounce.

"For the second time this year it looks as though markets have got a little ahead of themselves when it comes to predicting the outcome of a major vote," Oanda's Erlam added.

"Back in June the markets had all but priced in a UK vote to remain in the EU, this time it was a similarly favourable market outcome that traders were banking on - a Clinton victory - and it seems that once again, they may have got it wildly wrong."

High-yielding currencies in Asia-Pacific were battered against the dollar, with the South Korean won down 1.8 per cent, Australia's dollar 0.9 per cent off, Indonesia's rupiah down 1.1 per cent and the Malaysian ringgit 0.5 per cent lower.

Oil prices plunged, with WTI sinking 3.5 per cent and Brent three per cent down.

AFP