WASHINGTON - Billionaire populist Donald Trump was poised for a possible shock victory over Hillary Clinton in Tuesday's historic US presidential election, as a string of early gains for the Republican jolted world markets and stunned her supporters.
Ms Clinton -- the Democratic former first lady, senator and secretary of state -- began the day as the narrow favourite to win the White House and become America's first female president.
But as polls closed in all but the westernmost states, and media called state races one-by-one, giving the key battleground state Ohio to her Republican rival, pollsters were scrambling to update their forecasts and pointing to either a dead heat or an upset.
Within minutes, he also was declared the winner in Florida, which has 29 electoral college votes.
He also won North Carolina, another key state with 16 electoral votes.
With those wins, as of 11 am Thailand time, Mr Trump was leading Ms Clinton in the popular vote (49.4%-46.4%) and the Electoral College race, 223-209. Ms Clinton's electoral total includes states where no votes have been counted, including California and Oregon.
To win, Ms Clinton must win key states, and she is trailing in most vote-counting.
World markets plunged as US observers awaited results from key states Florida and Pennsylvania, with Mexico's peso plummeting in fear that Trump will make good on his vow to wall off America's neighbor to the south.
Safe haven assets rallied, with the yen and gold rushing higher, and Wall Street futures fell 2.6 percent in after-hours trade.
Clinton supporters who had gathered at a glittering reception in New York expecting to hear a victory speech from the pioneering 69-year-old Democrat fell quiet and jabbed nervously at their phones.
"Not great," muttered railroad retiree Joan Divenuti, who came all the way from Massachusetts to cheer her heroine. "Florida was always a problem," she added, as partial vote counts put Trump ahead.
Across town at the Trump election party, the 70-year-old property tycoon's supporters were tense but buoyant -- and a more well-heeled crowd than the blue-collar Midwesterners he is counting on for victory.
"This is like a football game. I'm going to have a heart attack," said 76-year-old Mike Garcia, a Republican from Pennsylvania.
At 10:00 pm (10 am Thailand time), Trump was projected to win 19 states worth 169 electoral college votes and Clinton had 11 including battleground Virginia plus the capital Washington, for 122 votes.
Victory goes to the first with 270 or more.