Protesters hold banner reading, ‘Antisemitism is treatable,’ during a counter-demonstration against a far-right rally in support of the Holocaust bill in front of the Presidential Palace in Warsaw, Poland, Feb. 5, 2018. Photo: Agencja Gazeta / Dawid Zuchowicz via Reuters.

Poland’s religious and political leaders should unequivocally condemn antisemitic behavior following a number of troubling events in the country, the head of the World Jewish Congress wrote on Wednesday.

Ronald S. Lauder criticized “the sight of protesters on the streets of Warsaw chanting anti-Jewish and anti-American slogans,” and the burning of an effigy of Judas in the Polish town of Pruchnik in April.

“We can’t allow for the ghosts of the past to rise again and to lead to the destruction of that which our nations have built over years,” he wrote in an op-ed published in Polish daily Rzeczpospolita.

Hundreds of far-right supporters marched in Warsaw on Saturday in protest against a US law on the restitution of Jewish property seized during or after World War Two, an increasingly prominent issue in Polish election campaigns.

The nationalist Law and Justice (PiS) government has said that, as a victim in World War Two, Poland should not be saddled with any financial obligations.

Poland was home to one of the world’s biggest Jewish communities before it was almost entirely wiped out by Nazi occupiers who set up death camps on Polish soil.

“Poles can’t and shouldn’t be blamed for the fact that Nazis chose Nazi-occupied Poland as the location for their death camps,” Lauder also wrote.

Poland will hold European parliament elections on May 26 and national elections in the autumn.