The Bosnian Serb government has disclosed for the first time the location of six new mass graves containing the remains of victims of the 1995 Srebrenica massacre, an official said. "We have presented a preliminary report to the government, informing them about the discovery of six new mass graves in the region of Srebrenica, based on information obtained from the defence and interior ministries," Milan Bogdanic, who heads a government-appointed commission, told AFP. Bosnian Serb authorities have until now refused to acknowledge the extent of the slaughter of some 10,000 Muslim men and boys -- the worst in Europe since World War II -- and have been accused of hindering the investigation by the international community. In 2002, the Bosnian Serb government issued a report minimizing the number of Srebrenica victims, triggering outrage among survivors and the international community. The commission, set up by the Republika Srpska (RS) or Bosnian Serb government to clarify what happened in the Bosnian town, has until mid-June to submit its final report. "The commission has already visited those sites," Bogdanic said. He said it was difficult to estimate the number of bodies since the new graves were secondary ones, to which Serbs transferred bodies from initial grave sites in a bid cover up the crime. A police source said that police accompanied commission members to the sites. So far more than 6,000 bodies have been exhumed from numerous mass graves around Srebrenica, but international officials have accused the Bosnian Serb government of withholding information on other burial sites and the fate of those still missing. The top international representative to Bosnia Paddy Ashdown said it appeared the commission had received an "improved cooperation from RS authorities and important new information" following sanctions he had earlier imposed for obstructing its work. However, Ashdown said his final judgment would have to wait until there had been a "thorough review." Ashdown sacked earlier this month several Bosnian Serb officials including Bosnian Serb army chief Cvjetko Savic for obstructing the commission's work. Meanwhile, Srebrenica survivors reacted cautiously to the information on new mass graves. "This will signal a change of attitude among Bosnian Serb authorities only if they are talking about new graves. Otherwise it is just an attempt to avoid sanctions," Munira Subasic of the Association of Srebrenica Mothers told AFP. Head of the Muslim-led commission for missing people Amor Masovic voiced hope that the six graves were not among twenty others locations of which were already known to his team. Top Balkan war crimes suspects, Bosnian Serb wartime leader Radovan Karadzic and his army chief Ratko Mladic, are charged with genocide by the UN war crimes tribunal in The Hague for their roles in the massacre after Serb troops overran the UN-protected eastern enclave. Both remain on the run enjoying large support among Bosnian Serbs many of whom still deny the massacre ever happened. Srebrenica also plays a central role in the charges against former Yugoslav president Slobodan Milosevic, on trial in The Hague for war crimes and crimes against humanity in connection with the Bosnian, Croatian and Kosovo wars. But nine years after the slaughter, the UN tribunal has sentenced only four people over Srebrenica while those thought ultimately responsible are still at large. And the Republika Srpska has yet to arrest a single war crimes suspect despite multiple UN indictments. In a historic decision, the UN tribunal ruled earlier this month that the Srebrenica massacre was genocide. Post-war Bosnia consists of two semi-independent entities -- the Serbs' Republika Srpska and the Muslim-Croat Federation. **PHOTO CAPTION*** A skull is unearthed in Kravice near Srebrenica in 1996. (AFP)