Anti-Semitic graffiti was spray-painted on a synagogue and several shops in north London overnight during the Jewish festival of Hanukkah.
The Jewish holy symbol alongside the numbers “9 11” was daubed in a number of locations across Hampstead and Belsize Park.
The graffiti references an anti-Semitic conspiracy theory that Jews are responsible for the 9/11 terror attack.
The Metropolitan Police say they are investigating a potential hate crime after receiving reports of the vandalism at 11.30pm on Saturday.
Conservative councillor for Hampstead Oliver Cooper said he spent Sunday morning patrolling the neighbourhood after “appalled” residents alerted the Community Security Trust (CST) charity, which works to protect the Jewish community.
“My first reaction was shock and horror,” Mr Cooper said.
“I’ve had to report anti-Semitic graffiti in Hampstead a number of times before, including by a banned neo-Nazi group, but I have never seen anything approaching this extent.”
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He added: “I was alerted to these incidents by a number of neighbours, who had reported it to the Community Security Trust.
“I spent this morning walking around Hampstead to find all the locations so that they could be removed as quickly as possible, and to reassure residents that were naturally appalled by it that the police and CST were already aware and taking it as seriously as it deserved to be.”
Mr Cooper said he came across the graffiti in nine places, and others also posted photographs of the markings on Twitter.
Labour MP for Hampstead and Kilburn Tulip Siddiq condemned the vandalism as “unbelievable, senseless, disgusting anti-Semitism at the heart of our community”.
She added: “I am in touch with Camden Council and Borough Commander (Raj) Kohli regarding clean-up and attempting to find these criminals – we must all stay vigilant in order to continue the fight against this hatred.”
Inspector Kev Hailes said: “This is clearly a concerning incident and one we are taking seriously.
“We have liaised with our partners in order to remove the graffiti and various inquiries are under way to find who is responsible.
“Officers will be on patrol throughout the area in order to provide some reassurance to local communities. Please approach us if you have any questions or concerns.”
The Metropolitan Police said no arrests have yet been made and have asked anyone who saw anything suspicious on Saturday night to call them on 101.