Bosnian Serb forces captured Srebrenica, then a designated U.N. "safe area", in July 1995 and killed more than 8,000 Muslim men and boys in the days that followed.
A Bosnian Muslim wartime commander who defended Srebrenica against separatist Serb forces pleaded not guilty on Monday to the killing of three Serb prisoners earlier in Bosnia's 1992-95 war.
Naser Oric's trial is highly sensitive in the ethnically divided Balkan country, where many Bosnian Muslims or Bosniaks regard him as a hero and Serbs think he is a war criminal.
Oric was acquitted of the charges by the International Criminal Tribunal for the Former Yugoslavia (ICTY) in 2008, but was arrested in June in Switzerland on a warrant from Serbia over the prisoner killings near Srebrenica.
He was extradited, however, to Bosnia, which insisted he should be tried in the country where the crimes allegedly occurred. He is being tried by a state court set up to handle war crimes cases, easing the burden on the ICTY.
Bosnian Serb forces captured Srebrenica, then a designated U.N. "safe area", in July 1995 and killed more than 8,000 Muslim men and boys in the days that followed. It was Europe's worst mass killing since World War Two and a U.N. war crimes tribunal said the massacre constituted genocide.
Oric, who had been in charge of organising Srebrenica's defence, and Bosnian Muslim soldier Sabahudin Muhic were indicted for the murder of three Serb prisoners in the villages of Zalazje, Lolici and Kunjerac in 1992.
"Your Honour, I am not guilty under any count of the indictment," Oric told the state court. The same plea was entered by Muhic, who is serving prison time for other offences.
Oric's lawyers said previously the Sarajevo court was trying him for the same crimes of which he had been acquitted by the ICTY in The Hague, but appeared more cautious on Monday.
"It is debatable," defence lawyer Lejla Covic told Reuters, declining to elaborate.