Hollande, Sarkozy head for French presidential runoff
Europe correspondent Philip Williams, wires
Socialist candidate Francois Hollande has beaten incumbent Nicolas Sarkozy into second place in the first round of France's presidential election.
Estimates show Mr Hollande has won between 28 and 29 per cent of the vote to Mr Sarkozy's 25.5 to 27 per cent.
The big shock was a strong showing for far-right candidate Marine Le Pen.
Ms Le Pen was third with between 18 and 20 per cent in an election dominated by concerns about the French economy and the crisis in the eurozone.
Although Mr Hollande had only a slim lead, analysts say he will have a commanding advantage when he faces Mr Sarkozy in the second round of voting in a fortnight's time.
Mr Sarkozy had warned a Socialist win would lead to an economic crisis, but Mr Hollande has promised to promote growth over austerity and increase taxes for the rich.
But the best ever showing of Ms Le Pen's National Front party has complicated forecasts for the second round and surprised France's political establishment.
The far-right politician, whose father Jean-Marie Le Pen founded the National Front, declared that "the battle of France has just begun" and said "we have exploded the monopoly of the two parties".
She said she would wait until May 1 before telling her supporters who to vote for in the run-off, with Mr Sarkozy expected to try to appeal to far-right voters to win the second round.
Meanwhile opponents of all stripes queued up to pronounce Mr Sarkozy's political obituary.
"I am today the best placed candidate to become the next French president," Mr Hollande told a large crowd in his constituency in central France.
"The second major lesson to draw from this election - and this is undeniable - is that the first round was a punishment and a rejection of the incumbent."
'Sarkozy is finished'
Mr Le Pen refused to say who he would vote for in the second round now that his daughter had been eliminated, but added: "I think Sarkozy is finished."
Mr Sarkozy's camp put a brave face on the defeat, insisting with the votes of the Le Pen camp and that of centrist Francois Bayrou the right had not had a bad night and that the president would bounce back before May 6.
"The message from the French, which we heard loud and clear, was that this was a vote in a time of crisis," said Jean-Francois Cope, leader of Mr Sarkozy's right-wing UMP and a possible future presidential candidate.
"From tomorrow morning, we will no longer be in a case of nine candidates against Nicolas Sarkozy, but we will be one-to-one, Nicolas Sarkozy against Francois Hollande... then I think the match will be different," he said.
Far-left candidate Jean-Luc Melenchon was beaten into fourth place with around 11.7 per cent, a disappointment for his supporters after a barnstorming campaign, and called on the left to unite to oust Mr Sarkozy.
Turnout was high at at least 80 per cent, down on the 84 per cent turnout of 2007, but up significantly on the 72 per cent of 2002 and belying fears that a low-key campaign would be capped by mass abstentions.
The left has not won a presidential election in a quarter of a century, but with France mired in low growth and rising joblessness, opinion polls had long predicted the left would beat the right-wing incumbent.
The eurozone debt crisis and France's sluggish growth and high unemployment have hung over the campaign, with Mr Sarkozy struggling to defend his record and Mr Hollande unable to credibly promise spending increases.
Opinion polls and campaigning were banned from midnight on Friday but have now resumed in the build-up to the May 6 run-off.
An opinion poll commissioned by French public television and the Le Monde newspaper after the first round predicted Mr Hollande would beat Mr Sarkozy by 54 to 46 per cent in the second round.