The former Bosnian-Serb army commander, Ratko Mladic, has described as "satanic" a UN court trying his former political master Radovan Karadzic, and said he would not give evidence at the trial.
His refusal on Tuesday is despite a subpoena issued by the International Criminal Tribunal for the former Yugoslavia, in the Dutch city of The Hague.
"I do not want to testify and refuse to testify for reasons of my health and that it would prejudice my own case," Mladic said, labelling the court "satanic".
Mladic, known as the "Butcher of Bosnia" for his alleged role in the Srebrenica massacre, has been called as a defence witness for Karadzic, the former Bosnian-Serb president.
Karadzic, who is representing himself, asked Mladic whether he had ever informed him that civilians at Srebrenica would be killed, that terror through shelling or sniping would be used in Sarajevo or that Serb areas would be ethnically cleansed.
Mladic refused to answer all the questions. He was speaking loudly in Serbian as he was finally escorted out of the courtroom after judges refused his request.
"You have confirmed my theory that the tribunal is not a court of law but a satanic court," Mladic said as he was led away.
Karadzic and Mladic both face charges over the massacre of almost 8,000 Muslim men and boys in the eastern town of Srebrenica in July 1995 as well as over the bloody 44-month siege of the Bosnian capital Sarajevo, which claimed an estimated 10,000 lives.
They could have been tried together had they been arrested around the same time. But Karadzic was arrested in July 2008 and Mladic in May 2011. Both men insist they are innocent.