Vandals desecrated at least 500 tombs of Muslim soldiers in northern France on Monday — an act President Nicolas Sarkozy denounced as "repugnant racism."

The desecration near the town of Arras appeared timed with the start of Eid al-Adha, the most important holiday in the Muslim calendar.

The administration for the Pas-de-Calais region said the damaged tombs were in the Muslim section of the Notre-Dame-de-Lorette cemetery, a well-groomed burial ground for World War I soldiers. Some had swastikas scrawled on the tombstone, others had lettering whose meaning was unclear.

There are 576 graves in the Muslim section of the cemetery, where more than 30,000 soldiers are buried.

Sarkozy, in a statement, said the "abject and revolting act" equates with "repugnant racism against France's Muslim community" and insults the memory of all World War I combatants.

It was the third time the Muslim section of the cemetery has been targeted. Last April, 148 tombs were desecrated, and a year before that 52 headstones and an ossuary were vandalized.

The French Council for the Muslim Faith, a group representing France's numerous Muslim groups, decried "these odious, revolting and scandalous acts" and said it expected authorities to find out who carried out the attack.

Interior Minister Michele Alliot-Marie said police were investigating the incident.