Socialist champion Francois Hollande stamped his authority on the French presidential race on Sunday, winning the first round of polling and setting up a May 6 run-off with incumbent Nicolas Sarkozy.

Hollande won between 28 and 30% of the vote in the first round, to Sarkozy's 24
to 27.5, according to estimates compiled from ballot samples by several polling agencies and obtained by AFP from multiple sources.

That made Sarkozy the only incumbent French president to lose a first round-vote in the history of the Fifth Republic, which came into being in 1958.

Official results were not to be made available until polls closed in major urban centres at 8:00pm (1800 GMT), but the tendency was clear and the mood at Sarkozy's campaign headquarters was resigned and sombre.

"It's a very good first round score. Dignity paid off," said Socialist spokeswoman Aurelie Filippetti, welcoming Sunday's result in the more upbeat venues of Hollande's party headquarters.

Ten candidates were in the race -- Hollande and Sarkozy being trailed by far-right flag-bearer Marine Le Pen, hard-left firebrand Jean-Luc Melenchon, veteran centrist Francois Bayrou and a handful of outsiders.

Le Pen came third with between 17 and 20%, beating bitter enemy Melenchon, who scored between 10.5 and 13%. Bayrou won between 8.7 and 10%, according to the estimates seen by AFP.