Israel's brutal assault on the Gaza Strip has prompted a wave of reprisal attacks against Jewish targets in Europe and community leaders fear a wider resurgence of anti-Semitic feeling.

In the most serious incident, assailants rammed a burning car into the gates of a synagogue in Toulouse, southwest France, last night.

There has other arson attack against Jewish congregation in Sweden and the UK and an organisation that provides self-defence advice for British Jews said that as many as 25 racist incidents over the past week could be linked to the Gaza conflict.

The latest attacks come after a hardline Hamas leader, Mahmoud Zahar, warned that the Islamists would kill Jewish children anywhere in the world in revenge for an assault in which more than 500 Palestinians have been killed, including at least 40 people taking shelter in a UN-run school hit in an air strike today.

Arabic television channels have screened images of Palestinian children killed or injured in Israel's assault on Gaza that have caused outrage in Muslim communities around the world.

In Denmark, a 27-year-old Dane born in Lebanon of Palestinian parents is alleged to have injured two young Israelis last week, opening fire with a handgun in a shooting that police suspect could be linked to the Gaza crisis.

Last night a Jewish congregation in Helsingborg, in southern Sweden, was attacked by someone who “broke a window and threw in something that was burning,” a police spokesman said. Neighbors alerted rescue services before the fire took

On Sunday slogans including “murderers ... You broke the cease-fire" and “don’t subject Palestine to ethnic cleansing" were daubed on Israel’s embassy in Stockholm.

France has Western Europe’s largest Jewish and Muslim communities and a history of anti-Semitic violence flaring when tensions in the Middle East are high. But President Sarkozy warned in a statement today that France would not tolerate violence linked to the Gaza crisis.

Damage to the synagogue in Toulouse was limited to a blackened gate, and there were no injuries even though a rabbi was giving a course to adults inside, authorities said. They said unlighted gasoline bombs were also found in a car nearby and in the synagogue’s yard.

A local Jewish leader, Armand Partouche, said he believed the assailants had planned to torch the synagogue, but fled when the building’s alarm went off. “It could have been very, very serious,” Mr Partouche said. "There were people inside; there could have been deaths.”

He said Jewish leaders are asking Toulouse authorities for reinforced security for the city’s synagogues. “We really fear that anti-Semitism will spring up again and that the current conflict will be transposed to our beautiful French republic,” he said.

In the UK, the Community Security Trust, a Jewish self-defence charity, said it had seen a rise in anti-Semitic incidents since the start of Israel’s offensive against Gaza. The group said it had recorded 20-25 incidents across the country in the past week that it believed were connected with Gaza, including an arson attempt on the Brondesbury Park synagogue in northwest London on Sunday.

Mark Gardner, a spokesman for the Trust, said that in another incident last week a gang of 15-20 youths walked along the main street in Golders Green, a largely Jewish neighborhood in north London, shouting “Jew" and “Free Palestine" at passers-by.

“It could get worse,” Mr Gardner said. “We tend to see these things happen in waves.”

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