Republican Donald Trump, a political outsider who was not given much chance till last week, won the US presidential election this morning, sweeping a series of key battleground states and surprising markets and analysts.

His Democratic rival Hillary Clinton called Trump to concede the election. She congratulated him on his victory.

His surprise showing at the polls rattled world markets that had expected Clinton to win.

In his vicotry speech, Trump congratulated Clinton on the hard fought election and thanked Clinton for her great service to the nation.

"It's time to come together as one of country. I pledge I will be president for the whole America," he said.

"We will get along with all nations that are willing to get along with us," he said. We will seek common ground and build partnership," he said.

"We must reclaim the country's destiny and we will rebuild it," he said.

The billionaire real estate magnate and former reality star needed an almost perfect run through the swing states -- and he got it, winning Ohio, North Carolina and Florida, said CNN.

The campaign he carried repeatedly shattered the conventions of politics and he pulled off a remarkable upset, it said.

Trump won with 289 electoral votes compared to 218 for Clinton, according to CNN projections.

Trump's supporters embraced his plainspoken style, assault on political correctness and vow to crush what he portrayed in the final days of his campaign as a corrupt, globalized elite -- epitomised by the Clintons -- that he claimed conspired to keep hard-working Americans down, CNN said.

His winning coalition of largely white, working-class voters suggests a populace desperate for change and disillusioned with an entire generation of political leaders and the economic and political system itself, it added.

The Trump win sent shock waves across world markets that had counted on a win by Clinton as investors worried a Trump victory could cause economic and global uncertainty.

The US dollar sank and stock markets slammed into reverse in wild Asian trade on Wednesday as every new exit poll in the US presidential election showed the race to be a nail-biter, sending investors stampeding to safe-haven assets.

Sovereign bonds and gold shot higher while the Mexican peso went into near free-fall as investors faced the real possibility of a shock win by Republican Donald Trump.

Gold climbed to $1,308.00 an ounce as the dollar slid. Oil turned tail, with US crude shedding $1.34 to $43.63 a barrel, while Brent fell $1.24 to $44.80.