Prime Minister Vojislav Kostunica's Democratic Party of Serbia said in a statement that neither Zagreb's nor Belgrade's nor the international community's responsibility had been determined after 11 years.
"What happened 11 years ago in the regions of Banija, Lika, Kordun and north Dalmatia had all the characteristics of ethnic cleansing," read the statement, adding that "nobody's guilt can be hidden".
Serbian Radical Party vice president Tomislav Nikolic told a news conference that marking the anniversary of the suffering of the Serb people "is hard for both the Serb people and for civilised Europe".
Nikolic accused Serbia's authorities of "maintaining extraordinary relations with Croatia, not caring that hundreds of Serbs from Krajina have no home and that enabling those expelled to return is furthest from Croatia's mind".
The August 1995 Operation Storm liberated the parts of Croatia which until then had been occupied by Croatian Serb rebels.