WARSAW, Poland (JTA) — Unknown vandals defaced the fence of a Jewish cemetery in Warsaw, considered to be one of the largest in Europe.

The attack on the Jewish cemetery on Okopowa Street in Warsaw was discovered on Saturday. Burials still occur in part of the cemetery.

The vandals wrote on the fence with red spray paint: “Jews for slaughter,” and the date 10.12.14. That is the day on which Poland’s Constitutional Tribunal ruled in the case of religious slaughter, when judges on the Tribunal decided that the ban on ritual slaughter was unconstitutional.

The gate of the cemetery was painted with yellow emulsion paint as well. The damage was discovered on Sunday by cemetery Director Przemyslaw Szpilman, who immediately notified police.

Szpilman said that he does not know if the vandalism is an “immature prank or a political issue.”

“Such incidents do not happen very often. In 2013, someone painted a swastika on the wall of the cemetery, but for the last 12 years nothing like that has happened,” he told JTA.

“Less than a week after the 70th anniversary of the liberation of Auschwitz-Birkenau, we have to deal with the manifestation of hatred against Jews.  ‘Jews for slaughter’ is not only a humiliation that society cannot ignore, it is an invitation to violence and threats to which we should all be vigilant,” said Anna Chipczynska, President of the Jewish Community of Warsaw.

“It is sad, that the deceased perish for the decisions of the living,” Piotr Kadlcik, former president of the Union of Jewish Religious Communities in Poland, told JTA.