Bosnian Serb leaders have apologised for the first time to relatives of up to 8,000 Muslims killed by Bosnian Serb forces in Srebrenica in 1995.
Many victims found in mass graves have been reburied
The government said it "sympathises with the pain of relatives of the Srebrenica victims and expresses sincere regrets and apologies".
Only last month, an official Bosnian Serb report admitted for the first time that more than 7,000 had been killed.
The UN war crimes tribunal in The Hague has described the massacre as genocide.
The killings happened after Serb forces stormed a UN-designated safe area near the end of the 1992-1995 war in Bosnia-Hercegovina.
The men and boys were forcibly separated from their families and killed, while the women, children and old men living in the town were deported. Many of the victims were buried in mass graves.
The government's apology spoke of the Srebrenica massacre as a "tragedy".
The statement follows its acceptance last month of the commission report into the massacre, which previously it had downplayed.
The Bosnian Serb (Republika Srpska) government said it supported trials for those responsible for the slaughter.
"The Republika Srpska government is committed and is undertaking decisive steps to bring to justice all those who committed war crimes," it said.
Although Bosnia-Hercegovina is now under international administration it is divided into two republics, one Serb, the other Muslim and Croat.
The BBC's Belgrade correspondent Matt Prodger says that despite the apology for Srebrenica, the Bosnian Serb Republic has been harshly criticised for failing to arrest a single war crimes suspect.
The Bosnian Serbs' political leader during the 1992-95 war, Radovan Karadzic, and his military commander, Ratko Mladic, are still on the run.
Both men have been indicted by the UN tribunal for war crimes and genocide for their alleged roles in the Srebrenica massacre, but they remain at large somewhere in the former Yugoslavia.