Update 8pm: Far-right leader Marine Le Pen and centrist candidate Emmanuel Macron are leading in the first round of the French presidential election, polling agency projections show.
The results could set up a duel between a young candidate with no electoral experience and the woman who remade the image of a party tainted by racism and anti-Semitism.
As polls across the country closed, projections put far-left contender Jean-Luc Melenchon and conservative Francois Fillon just behind the front-runners.
The two candidates who secure the most votes in Sunday's first round will contest a May 7 head-to-head run-off ballot.
If Ms Le Pen and Mr Macron's leads hold, it would be the first time in modern French history that no major party candidate has advanced to the final vote.
Supporters of Ms Le Pen and Mr Macron went wild with cheers as the projections were revealed.
"We will win!" Le Pen supporters chanted in her election day headquarters in Henin-Beaumont. They burst into a rendition of the French national anthem, and waved French flags and blue flags with "Marine President" inscribed on them.
Mr Macron supporter Mathilde Julien said "he represents France's future, a future within Europe".
Meanwhile at the base of Mr Fillon in Paris, silence and disappointed sighs rose up as the projections appeared on TV screens.
Socialist candidate Benoit Hamon has conceded defeat after the projections showed him to be in a distant fifth place.
Mr Hamon said as he acknowledged losing the race that "the left is not dead", and he urged voters to back Mr Macron on May 7.
Mr Fillon has also conceded defeat, and called on his supporters to now back Mr Macron.
French Prime Minister Bernard Cazeneuve also urged voters to support Mr Macron as he greeted the projections with a call for the defeat of Ms Le Pen's National Front party.
Voter turnout in France's knife-edge presidential election is above 69% - almost as high as the last such ballot.
The Interior Ministry said turnout reached 69.4% well before polls closed, which compares to 70.6% in the first round of presidential voting in 2012.
After years of economic stagnation and high unemployment, voter disillusionment is exceptionally high this year, which had prompted expectations of lower-than-usual turnout.
Polls have suggested far-right candidate Marine Le Pen's voters were especially motivated to cast ballots, while supporters of other candidates were less convinced.
Sunny weather in much of France may have played a role, while some pollsters also said the attack on police in Paris on Thursday may have prodded voters into taking part in the election.
More than 50,000 police and gendarmes were deployed to the 66,000 polling stations for the election, which comes after Thursday's deadly attack on the Champs-Elysees in which a police officer and the gunman were killed.
Voters are choosing between 11 candidates in the most unpredictable contest in decades.
Opinion polls point to a tight race among the four leading contenders vying to advance to the May 7 presidential run-off, when the top two candidates will go head to head.
Polls suggest Ms Le Pen and Emmanuel Macron, an independent centrist and former economy minister, are in the lead.
However, conservative Francois Fillon, a former prime minister who was embroiled in a scandal over alleged fake jobs, appears to be closing the gap, as is far-left candidate Jean-Luc Melenchon.
France's 10% unemployment rate, its struggling economy and security are issues that top concerns for the 47 million eligible voters.
The election is also widely seen as a vote on the future of the European Union - with most of the candidates railing against its institutions.
Both Ms Le Pen and Mr Melenchon - two candidates from opposite ends of the political spectrum - could pull France out of the 28-nation bloc and its shared euro currency in a so-called "Frexit".
Mr Melenchon has said that is a possibility if he cannot renegotiate France's role in a bloc blamed for economic and security woes.
Mr Macron and Mr Fillon are committed to European unity and would reform employment rules.
Metres from the polling station where Ms Le Pen was heading to vote, several feminist activists from the Femen group were arrested after staging a topless protest against the far-right leader, who is the only major female contender in the race.
Police intervened and stopped the commotion minutes before the 48-year-old arrived to cast her ballot in the northern town of Henin-Beaumont. No-one was hurt.
Mr Macron, meanwhile, was the image of serenity as he posed for selfies with voters after casting his ballot in the coastal town of Le Touquet in northern France alongside his wife Brigitte Macron.
Mr Fillon voted in Paris but his Welsh-born wife Penelope - who has been handed preliminary charges for her role in the fake jobs scandal that rocked her husband's campaign - voted 155 miles away from him near their 14th-century manor house in Sarthe.