Republican candidate Donald Trump is edging closer to the US presidency after a string of stunning victories over Hillary Clinton in swing states.
He won Florida, Ohio, Iowa and North Carolina, while Democrat Mrs Clinton took Virginia and Nevada, ABC projects. Pennsylvania is too close to call.
New Hampshire, Michigan and Wisconsin - which were meant to be part of the Clinton firewall - are cliffhangers.
Markets lurched as Mrs Clinton’s path to victory began to narrow.
The US dollar and Mexican peso plummeted while the Dow futures dropped 800 points.
Mr Trump is closing in on the 270 out of 538 electoral college votes needed to declare victory.
The mood is dark at Mrs Clinton’s election night party in New York City.
Clinton campaign chairman John Podesta signalled she was not ready to concede, telling the party faithful: "She is not done yet."
But supporters were crying and staring stony-faced at the big screens showing election results.
At Trump headquarters across town, his fans were cheering and chanting about the Democratic nominee: "Lock her up!"
Hillary Clinton’s supporters thought they’d arrived for a victory party, and the roofing at the convention centre in New York doubled as a metaphor - a giant glass ceiling ready, symbolically at least, to be shattered.
But under it the mood fast changed to concern and fretfulness as early all-important swing states, like Florida and Ohio, went to Donald Trump. Nervousness turned to utter disbelief as reliably blue Democratic states like Michigan and Wisconsin looked to be turning red.
The famed blue wall, which has made the Democrats so strong in presidential politics, looked to be crumbling before their eyes. Now the mood is one of despair.
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Mr Trump earlier racked up wins in the Midwest and South, while Mrs Clinton swept the Northeast, ABC News projects.
As expected, the Republican candidate was victorious in the Republican strongholds of Utah, Alabama, Kentucky, South Carolina, Nebraska, Indiana, West Virginia, Mississippi, Tennessee, Oklahoma and Texas, ABC projects.
And he took Georgia, Missouri, Montana, Louisiana, Arkansas, Kansas, North Dakota, South Dakota, Idaho and Wyoming - all solidly conservative states.
Mrs Clinton won the Democratic heartlands of California, Oregon, New York, New Jersey, Connecticut, Massachusetts, Maryland, Vermont, Delaware, Illinois, Rhode Island, Hawaii, Washington, Maine and District of Columbia, as well as New Mexico and Colorado.
Mr Trump, a 70-year-old Manhattan real estate tycoon, and Mrs Clinton, who is 69 and would be the first female US president, voted on Tuesday in New York City.
The Republican was booed as he arrived to cast his ballot at a school in Manhattan, alongside his wife, Melania, and daughter, Ivanka.
The two presidential hopefuls are spending election night in New York City, staging events barely a mile apart.
Mrs Clinton was due to address supporters at the Javits Centre in Manhattan, while Mr Trump holds an event at the Hilton Midtown hotel.
More than 5,000 police officers have been deployed across America’s biggest city to keep order on election night.
On Tuesday, Mr Trump again declined to say whether he will accept the results.
"We’re going to see how things play out," he told Fox News, while alleging there had been voting irregularities. "I want to see everything honest."
Some polling locations have reported equipment failures and long lines, but they appeared to be routine problems.
Mr Trump, who stoked conspiracies over the legitimacy of the democratic process during the campaign by claiming the vote would be "rigged", also filed an emergency lawsuit in Nevada.
The Republican’s camp sued the Clark County Registrar of Voters, alleging the state had kept early voting stations open late.
But a judge rejected the request.
All 50 states and Washington DC voted across six different time zones.
Americans also had a chance to determine which party holds sway in Congress.
All 435 seats in the House of Representatives were up for grabs, and a third of seats in the Senate, but Republicans looked likely to keep control of both chambers.
A record number of Americans - more than 45 million - voted early by post or at polling stations.
Mr Trump, a populist political newcomer, provoked controversy on the campaign trail for comments about women, Muslims and a plan to build a wall along the US-Mexican border.
Mrs Clinton saw her campaign dogged by FBI investigations into whether she abused state secrets by operating a private email server during her time as US secretary of state.
Last Sunday, the law enforcement bureau cleared her once again of any criminality.
Mr Trump and Mrs Clinton are seeking to succeed Democratic President Barack Obama.
After two four-year terms in the White House, he is barred by the US constitution from running for re-election.