WASHINGTON: Billionaire populist Donald Trump, tapping into an electorate fed up with Washington insiders, was on the verge of a shock victory Wednesday over Hillary Clinton in a historic US presidential election that sent world markets into meltdown.

State-by-state, one-by-one, the 70-year-old maverick Republican tycoon racked up victories in defiance of the forecasts of pundits and pollsters, before arriving within striking distance of the White House.

Key races in Michigan and Pennsylvania remained to be called at 0630 GMT, but the 69-year-old Democrat’s supporters were in a state of shock and the markets did not wait for a concession speech to react.

US futures markets fell five percent in after-hours trading, mirrored by falls in London and Tokyo as the news broke that the world’s greatest economy could soon be in the hands of an untested protectionist.