Socialist Francois Hollande and conservative President Nicolas Sarkozy are heading for a run-off in the race for France's presidency.
On Sunday voters also handed a surprisingly strong third-place showing to far-right candidate Marine Le Pen.
The contest, to be resolved in the run-off on May 6, could alter the European political landscape as the continent deals with a financial crisis.
Mr Hollande was in the overall lead, amid widespread disappointment with Mr Sarkozy's first term and a sense that the incumbent favours the rich when the country is struggling with unemployment and bleak economic prospects.
Latest figures show Hollande took 28 per cent of the vote to Sarkozy's 27 per cent.
The National Front's Marine La Pen's won almost a fifth of the vote - the best result in modern times for France's far right. The candidates of the left and centre trailed further behind.
Following his first round victory, Francois Hollande told his supporters:
Speaking after the result, French President Nicolas Sarkozy has vowed to tighten border controls, control immigration and fight crime as he launched his campaign for the presidential election run-off following a record first-round vote for the far right.
Le Pen's unexpectedly high score reflected a surge in anti-establishment populist parties in many euro zone countries from the Netherlands to Greece as the debt crisis bites.
Voter surveys show about half of Le Pen's supporters would back Sarkozy in a second round and perhaps one fifth would vote for Hollande, making her a potential kingmaker in the run-off.
James Mates reports from Paris on early results from the French elections which show sitting President Nicolas Sarkozy trailing his Socialist rival, while there has been a surprise surge in support for the far-right.
Turnout was also surprisingly high.
The Interior Ministry said early turnout figures showed 70.6 per cent of France's 44-million-plus voters cast ballots before 5pm - less than the 73.8 per cent in 2007 at the same time, but more than in the four previous races.
Overall turnout in the 2007 first round was nearly 84 per cent, the highest figure since the 1970s.
With 93% of votes counted so far, here is the breakdown:
- Hollande won 28% of ballots cast
- Sarkozy won 27%
- Le Pen received 18.3% of votes: the best showing ever by the far right National Front party