Anti-Israel graffiti was daubed on a centre used by a messianic Jewish community in response to the Gaza conflict.
“Zionist killers of Palestinian children” and other offensive phrases were painted on the council-run building in Donaghadee, County Down, east of Belfast, where the Shalom Messianic Congregation meets twice a month.
The community was set up in May 2007 and has not previously been the target of an attack.
Congregation leader Jim Clint said: “There are not too many people outside our group who would know we are there. It’s baffled me as to who could have done it, but it’s clearly someone anti-Israeli. It’s very upsetting and to begin with I kept it from many of our older members.”
He said congregants bring items including Israeli flags, a menorah and a shofar to their services and it was possible someone had seen them arriving at the centre with their belongings.
A council spokeswoman said: “As is our policy when this kind of offensive graffiti appears on our property, it was removed as quickly as possible, in this case, on the same day.”
A CST spokesman added: “This incident shows the extent to which so-called anti-Zionism is now leading to intimidation and harassment of anyone deemed to be a Zionist.”
In London, a billboard advertising a Jewish dating website was also defaced with the words “F*** off you racist, Jewish bigots” last week.
The poster, outside a tube station in West Hampstead, north west London, was reported to Camden Council, which removed it.