French President Jacques Chirac on Saturday condemned what authorities say are likely arson attacks on two Muslim places of worship and vowed to track down those responsible.
The separate attacks in the south-eastern town of Annecy on Friday badly damaged a mosque and a Muslim prayer centre. There were no injuries and no-one has claimed responsibility.
An inquiry is underway.
"The president was very shocked to learn of the attacks on a mosque and a prayer centre. He strongly condemns these odious acts," Chirac's office said in a statement.
"He wishes to express his sympathy and solidarity with all Muslims in France and assures them of the determination of the public authorities to seek and punish the perpetrators of these attacks," it said.
French television showed a crowd of almost 300 demonstrators gathered outside the mosque on Saturday, with some voicing fears the attacks were inspired by anti-Islamic feeling.
France's law banning headscarves in state schools has just passed its final parliamentary hurdle. The ban, which also outlaws Jewish skullcaps and large Christian crosses, is aimed at quelling a perceived rise in radicalism among youths.