Lille were made to settle for a share of top spot as they were held to a 1-1 draw by Lyon.
Needing victory to move clear of Rennes at the top, Lille led through Moussa Sow's early strike. But Kim Kallstrom levelled after 26 minutes and that is how it stayed, leaving Lille top by goal difference alone with 46 points after 25 games.
Andre Ayew snatched a late goal as Marseille came from behind to beat Nancy 2-1 and move to within a point of the Ligue 1 summit.
The champions continued their strong recent form, notching a fourth straight league win to move level with Lille, one point behind Lille and Rennes.
Nancy took a 34th-minute lead through Julien Feret's outstanding solo effort, but Marseille equalised through Ayew on the stroke of half-time before the Ghanian grabbed a second four minutes from time.
Paris St Germain strengthened their chase of the Ligue 1 leaders with an entertaining 2-1 victory over Toulouse. They are now two points off the top.
First-half goals from Sylvain Armand and Mathieu Bodmer put the capital club in control. And Paulo Machado's earlier penalty miss ensured Toulouse remain winless away from home in 2011, despite Franck Tabanou's second-half goal.