A major European Jewish organisation has called on European governments to ban Greece's far-right Golden Dawn party, which received 7 percent of the vote and 21 seats at parliamentary elections.
Moshe Kantor, president of the European Jewish Congress, met Czech Prime Minister Petr Necas to seek support on adopting measures to tackle anti-Semitism on the continent.
He expressed concern about Golden Dawn, a neo-Nazi party in Greece whose leader, Nikos Michaloliakos, recently claimed that Nazi concentration camps did not use gas chambers and ovens to exterminate Jews.
"There were no ovens - it's a lie. I believe it's a lie. There were no gas chambers either," Michaloliakos said in an interview with Greece's private Mega TV channel. He added that 6 million Jews murdered in the Holocaust was an exaggeration.
Kantor said Golden Dawn's "political rise should have sent shock waves through Europe".
"Before calling on European leaders to act against hate on the street, they must clear their own house and that means banning and ostracising any politicians and political parties that preach hate and violence," AP reported Kantor as saying.
"While we highly value freedom of speech, we all recognise that there must be restrictions, and the visceral hatred propagated by the Golden Dawn is surely outside the boundaries of appropriate political discourse."
The Central Board of Jewish Communities (Kis) called on the Greek government to "condemn and isolate the forces seeking the revival of the darkest ideology of the European history", claiming those comments were an "insult" to the historical memory of the Jews who were murdered.
"It is an insult to the historical memory, the memory of the 6 million Jews, our brethren, amongst whom there where 70,000 Greek Jews, who perished in the death camps of Auschwitz, Dachau, Treblinka and the other sites of the extermination factory founded by Adolf Hitler," Kis said in a statement.
"It is an insult toward the survivors, who are still alive to bear witness of this atrocity. It is an insult toward all those who fought against the Nazis. It is an insult to the history of Greece, the sacrifices of the Greek people and the struggle to defend the principles of freedom, democracy and humanism."
Michaloliakos rejected any affiliation with Nazism, even though the party's emblem, a squared spiral, and its colours closely resemble the swastika.
He also made a Hitler-style salute when elected to Athens city council in 2010.
The far-right party appealed to nationalist sentiment rising in the country after the austerity measures demanded by the European Union and the IMF helped plunge Greece into further economic turmoil.
Golden Dawn's anti-immigration campaign was based on the slogan "So we can rid this land of filth".
"No one should fear me if they are a good Greek citizen. If they are traitors - I don't know," Michaloliakos said.
For further news on Anonymous's recent activities, check out the IBTimes UK Cyber Warfare section.