Attackers rammed a burning car into a synagogue in the southern French city of Toulouse, officials have said.
The car, packed with a petrol bomb, was set alight and then pushed into the synagogue door by a second car.
The building caught fire but a local rabbi and about 12 people caught inside escaped unharmed after Monday's attack.
It came as the French defence minister met Jewish and Muslim community leaders to stress the Middle East conflict should not lead to violence in France.
Police said they were investigating the attack and had not made any arrests.
Damage to the synagogue building was limited to a blackened door, a regional official said, adding that no-one was injured even though a rabbi was inside overseeing an adult learning course.
Anne-Gaelle Baudouin said police called to the scene found remnants of a Molotov cocktail in the burned-out car and found another car nearby containing three more unused petrol bombs.
Correspondents say it is not clear whether the incident reflects frustration in France as violence in the Middle East escalates.
Anti-Semitic violence in France - which has large Jewish and Muslim communities - rose sharply in 2002 when Israel launched large-scale military operations in the West Bank.
Large number of French Jews chose to emigrate to Israel in the wake of attacks on Jewish people or buildings.
The National Bureau for Vigilance against Anti-Semitism, a Jewish group, condemned the latest attack.
Dominique Sopo, the head of France's main anti-racist movement SOS Racisme, also condemned the fire-bombing, but said it was "most likely" linked to situation in the Gaza Strip.
"Those who want to import the Middle East conflict over here aren't helping the Israelis or the Palestinians, unless they can explain why hitting a Jew here improves the situation in Gaza, or how Arab-bashing helps protect Israel."
Meanwhile, French President Nicolas Sarkozy is on a two-day mission to the Middle East to try to secure a ceasefire in Gaza.