Heavy fighting has for the first time spread to the centre of Gao, the main city in northern Mali.
French troops are reported to be using artillery against rebels who have entered the city.
Clashes, which began near the central police station, have spread to other parts of the city.
Earlier, a suicide bomber blew himself up near a checkpoint at a northern entrance to the town - the second such incident in two days.
Gao was retaken on 26 January by French and Malian forces.
France now has about 2500 troops in Mali, since entering the conflict on 11 January.