Amid escalation of violence in the troubled Gaza strip, three youths have tried to torch a synagogue in London, police said on Wednesday.
There are also reports that Islamic extremists are drawing up a "hit-list" of Britain's leading Jews, bringing the Middle East conflict terrifyingly close to home.
According to police, arsonists first tried to smash open a window of a synagogue at Brondesbury Park in northwest London but failed because of the toughened glass in place to protect such buildings from terrorist attacks.
Having been thwarted, they tried to set the front door of the building alight with petrol, causing some damage to the exterior of the premises, Mark Gardner of the Jewish Charity, said.
Meanwhile, according to a report in The Sun on Wednesday, the TV channels apprentice boss Sir Alan Sugar, Amy Winehouse and Mark Ronson are among other prominent names who found a place the extremists hit-list.
Labour Peer and friend of former prime minister Tony Blair, Lord Levy, foreign secretary David Miliband and Princess Diana's lawyer Anthony Julius are also understood to be potential targets.
British anti-terror expert Glen Jenvey said online forum Ummah is being used to prepare a deadly backlash against UK Jews.
His warning came as Europe was hit by anti-Semitic attacks over Israel's push into the Gaza strip.
On the Ummah site, "Saladin1970" asks for help compiling "a list of those who support Israel".
"Abuislam" asks: "Have we got a list of top Jews we can target? Can someone post names and addresses?"
Saladin1970 gives a link to the Power 100 list of top British Jews.
Al-Qaeda's second-in-command Ayman al-Zawahiri called on Muslims on Tuesday to strike Western and Israeli targets "wherever you can".
Hamas leader Mahmoud Zahar urged the murder of Jewish children, saying Israel "legitimised the killing of their people all over the world".
The Community Security Trust, which advises Britain's Jewish community on safety, said: "We are advising prominent Jewish individuals to be conscious of potential threats."
The group has recorded 24 anti-Jewish incidents since December 29, including the arson raid on the London synagogue.
There have been synagogue attacks in France and Sweden also.