Judges trying ex-Bosnian Serb army chief Ratko Mladic turned down Thursday a prosecution bid to hold two separate trials, the first focusing on the Srebrenica massacre.

"The Trial Chamber today denied the Prosecution's request to sever the indictment against Ratko Mladic," a statement said, upholding a challenge filed by Mladic's lawyer Branko Lukic against the prosecution bid.

Splitting the proceedings in two "could prejudice the accused, render the trial less manageable and less efficient, and risk unduly burdening witnesses," the judges said.

Mladic, also named "the Butcher of Bosnia" is on trial on 11 counts of genocide, war crimes and crimes against humanity for his role in Bosnia's 1992-95 war.

Among other charges, the 69-year-old former general is accused of masterminding the murder of some 8,000 Muslim men and boys over a six-day period at Srebrenica in July 1995, in Europe's bloodiest episode since World War II.

Prosecutor Serge Brammertz had asked in August for the trial to be split in two -- one dealing solely with the Srebrenica massacre and the second with the rest of the charge sheet, including the siege of Sarajevo which claimed some 10,000 lives.