With 99.9 percent of ballots counted, socialist Francois Hollande has 28.61 percent of the vote, while his main rival conservative President Nicolas Sarkozy comes second with 27.08 percent, the Interior Ministry said on Monday, RIA Novosti reported.
Far-right candidate Marine Le Pen came third with 18.05 percent, beating far-left firebrand Jean-Luc Melenchon, who scored 11.12 percent. Centrist Francois Bayrou was fifth with 9.11 percent.
The five other candidates received minimal support of 2 percent or less.
French Interior Minister Claude Gueant said no major incidents were reported during Sunday's vote.
The turnout was about 80%, one of the highest results in the history of the Fifth Republic, founded by Charles de Gaulle in 1958.
The Interior Ministry is set to publish official results before 20:00 local time on Wednesday.
Surveys made after polling stations closed on Sunday show that Hollande is likely to defeat Sarkozy in the runoff.
A survey by CSA, conducted for the BFMTV channel, RMC radio station and the 20 Minutes newspaper, says that Hollande will receive 56 percent and Sarkozy - 44 percent.
An Ipsos survey for France Television, Radio France and Le Monde gives slightly difference figures of 54 percent for Hollande versus 46 percent for Sarkozy.
Ifop says in its survey for Europe 1 radio station, Paris Match magazine and Public Senat TV channel that Hollande and Sarkozy will get 54.5 and 45.5 percent of the vote, respectively.