Unknown attackers have daubed swastikas on 15 Muslim graves at a military cemetery in Strasbourg, north-east France, the interior ministry said on Friday.
Interior Minister Dominique de Villepin condemned the attack, which happened overnight and which comes after a string of attacks against Jewish, Muslim and Christian property in the region. Some 300 graves have been desecrated in recent months.
"All resources are mobilised to identify and pursue the authors of this particularly serious act," Villepin said in a statement.
Abdellah Boussouf, rector of the Strasbourg mosque, demanded more forceful government action.
"I can no longer be content at this stage with the condemnations and pledges of solidarity of political rulers. I want results," Boussouf told reporters.
"France's Muslims as a whole have the feeling they are considered second-class citizens," he added.
A desecration of Muslim graves in Strasbourg in June prompted French President Jacques Chirac to announce a new drive to end ethnic intolerance in France.
Villepin visited local Muslim leaders after that attack to announce the creation of an interfaith committee to work towards greater tolerance and understanding.
France, home to Western Europe's biggest Jewish and Muslim communities, has also seen a rise in anti-Semitic attacks in recent years, which some blame on tensions stoked by the Middle East conflict.