Anti-fascists and Jews boycott Croatia memorial at WWII death camp
Activists hold an anti-fascist banner at a ceremony for the death camp victims of Croatia's former Nazi-allied regime (AFP Photo/STRINGER)

Croatia honoured on Sunday the victims of its most brutal World War II death camp, an event again snubbed by ethnic Serbs, Jews and anti-fascists who accuse authorities of tolerating a pro-Nazi ideology.

Conservative Prime Minister Andrej Plenkovic, several ministers and foreign diplomats attended a commemoration ceremony at the site of the Jasenovac camp which was dismantled 72 years ago.

Letters by survivors of the camp known as "Croatia's Auschwitz" -- a reference to the German World War II death camp in Poland -- were read during a ceremony that concluded with a multi-denominational service and laying of wreaths.

The camp, some 100 kilometres (60 miles) southeast of Zagreb, was run by the country's Nazi-allied Ustasha regime which persecuted and killed hundreds of thousands of ethnic Serbs, Jews, Roma and anti-fascist Croatians.

But for a second straight year, representatives of those groups boycotted the official commemoration, denouncing what they see as a resurgence of pro-Ustasha sympathies and instead organised their own separate events.

On Saturday, several thousand people including survivors of the camp, victims' relatives and foreign diplomats attended a ceremony organised by anti-fascists and ethnic Serbs.

"We cannot and will not accept the reluctance of authorities regarding ... the Ustasha regime's character and (the) policy of non-reaction to its symbols," the head of an anti-fascist association Franjo Habulin said.

Anti-fascists, ethnic Serbs and Jews in particular are incensed by a plaque with the Ustasha slogan "For the Homeland Ready" unveiled at Jasenovac in November.

It was created as a memorial by former paramilitaries to honour fellow fighters killed in the region at the start of Croatia's independence war in the 1990s.

Jews in Croatia are to hold their separate commemoration on Monday.

Plenkovic, who took power after snap elections in October, has pledged to move away from the climate of intolerance seen under his centre-right predecessors.

But critics say his administration has not done enough to tamp down extremism and expressions of nostalgia for the country's pro-Nazi past.

During Sunday's ceremony at Jasenovac, a group of anti-fascist activists displayed a large banner that read "Remove the Ustasha Salute".

Meanwhile, Serbian Prime Minister Aleksandar Vucic paid respect to the camp's victims in neighbouring Bosnia where part of the Jasenovac complex was located.

"The killings were official and welcomed, it was a state crime," Vucic told a gathering that included other Serbian and Bosnian Serb officials, Serbian Orthodox Church Patriarch Irinej and camp survivors.

"We are witnessing attempts to resurrect the Ustasha ideology," Vucic said.

Jasenovac was the largest and most notoriously brutal of Croatia's death camps, where many inmates were killed by hammers, knives and stones.

The total number of people killed there remains disputed. It varies from tens of thousands to 700,000, according to Serbian figures.