Billionaire Donald Trump has won the New Hampshire primary in the Republican race for US presidential nominee.
Left-wing Vermont Senator Bernie Sanders has taken the Democratic vote, pushing ahead of former Secretary of State Hillary Clinton.
It marks a dramatic win for two outsider candidates who have made rallying against mainstream politics central to their campaigns.
State officials predicted a historic turnout in the New Hampshire vote.
It is the second state to vote following last week’s Iowa caucuses won by Texas Senator Ted Cruz for the Republicans and Mrs Clinton for the Democrats.
Mrs Clinton has congratulated Mr Sanders, but said in a speech she would continue to fight for every vote in the campaign. Ohio Governor John Kasich came second in the Republican race, with former Florida Governor Jeb Bush and Mr Cruz still vying for third place.
The primary gives momentum to the winners heading on to the next contests in South Carolina and Nevada.
Mr Trump’s lead in New Hampshire is the first time the New York businessman – who has never held elected office – has translated his widespread support in opinion polls into actual votes.
Early votes counted show Senator Sanders with a double-digit percentage lead over Mrs Clinton. He had led in the polls in New Hampshire for months, but it is still a significant victory for the self-described Democratic socialist candidate.
Analysis: Anthony Zurcher, BBC North America reporter in New Hampshire
Donald Trump is back, and Bernie Sanders is booming. That’s the clear takeaway from a New Hampshire primary night that ended with little drama at the top. Both the New York billionaire and the Democrat who derides the billionaire class appear posed to confirm their consistently large opinion poll leads here with double-digit wins.
For the last few weeks the drama on the Republican side has been the identity of the candidate who will finish second – and perhaps become the establishment candidate to take on Trump and Iowa caucuses winner Ted Cruz.
For a while it looked like that man would be Florida Senator Marco Rubio, but he seems destined for a middle-of-the-pack finish after a flop in Saturday’s debate. Instead it could be John Kasich. But the Ohio governor has little in the way of campaign infrastructure set up in the southern states that vote next in the primary process.
Tuesday’s results is likely to lend little clarity to the question of who gets the backing of mainstream Republicans. That’s good news for Mr Cruz and Mr Trump, who will benefit from a fractured establishment field for at least a while longer.
After the projections were announced, Mr Sanders tweeted: “When we stand together, we win. Thank you, New Hampshire!” He also urged his supporters to “stay in line” and continue voting, amid long queues and traffic outside polling stations.
Hillary Clinton’s campaign manager, Robby Mook, said in a memo that they expected the race for the Democratic nomination “very likely” to be decided in March.
The former secretary of state acknowledged before the polls that Mr Sanders had a natural advantage in New Hampshire because he represents the neighbouring state of Vermont as senator.
Mrs Clinton, who has more support from the Democratic establishment, narrowly won in Iowa.
Most polls closed at 19:00 local time (midnight GMT).
What are primaries and caucuses?
- They are the first contests in the US presidential race in which states decide who becomes each party’s official candidate
- Caucuses are a series of private meetings in which voters express support for candidates with a show of hands. Usually only registered voters, affiliated with a specific party, can take part
- Primaries are run by state governments and voting is done in a secret ballot
- Each primary or caucus earns delegates for the winning candidates who then vote for them at party conventions in July in which the final candidates are formally confirmed