Arsonists have rammed a synagogue with two cars packed with petrol bombs in the southern French city of Toulouse, local officials said.
One car was set on fire and pushed by the other until it hit the door of the synagogue, at a time when about a dozen people were attending a class with a rabbi.
The building caught fire but all those inside escaped unharmed.
Police found unexploded petrol bombs inside the second car, which did not catch fire.
They said they were investigating the attack, which took place on Monday night, and had not made any arrests.
Michele Alliot-Marie, France's interior minister, branded the attack "stupid and revolting" and admitted she was concerned that Israel's current offensive in the Gaza Strip could increase communal tensions in France, home to Europe's largest Arab and Jewish populations.
"I am, in fact, worried by the international situation," she told French radio.
"My concern is that the situation should not degenerate in our country, that the violence not be imported."
Luc Chatel, a government spokesman, said that the country's security forces were now in a state of increased vigilance.
Leila Shahid, the Palestinian envoy to the European Union, said she had no doubt that the attack was linked to rising anger among France's five million Muslims at news coming from the conflict.
"Look at the awful incident yesterday in Toulouse with this car rammed into a place of worship, which is unacceptable, but a result of images from Gaza," she told the same radio station.
Dominique Sopo, the head of SOS Racisme, France's main anti-racist movement, also condemned the arson ttack in Toulouse.
He said: "It's most likely that this crime is linked to the 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
Richard Prasquier, the head of an umbrella body of Jewish groups, said in an interview with France's Le Figaro newspaper that aggressive behaviour by some protesters at pro-Palestinian marches had worried him.
"We must really not import the conflict here. It must not, it cannot happen," he said.
The Union of Jewish Students in France has recorded two attacks on kosher stores in Bordeaux, one on a Jewish apartment in Paris and another on a synagogue in Toulon since New Year's Eve.
"We must not allow the Middle East conflict to shatter our lives together," the group warned in a statement.
France's National Bureau of Vigilance Against Anti-Semitism also raised the alarm over an attack on a rabbi's car near Paris last week, as well as a spike in "menacing" anti-Jewish posts in French internet chatrooms.
Nicolas Sarkozy, the French president, is currently visiting the Middle East in a bid to encourage a ceasefire between Israel and the Palestinian group Hamas.
But despite his condemnation of Israel's land offensive in Gaza, he remains deeply unpopular with many young people of Arab origin for his perceived hardline stance as interior minister before he became president.
In Britain, Jewish community groups have also said that the crisis in Gaza had provoked a surge of anti-Semitic intimidation and violence.
On Saturday, three youths tried to set fire to a synagogue in northwest London.
Police said that officers were liaising closely with Jewish groups and that "reassurance patrols" had been increased in areas with substantial Jewish populations.