The former Bosnian Serb army commander, Ratko Mladic, has criticised as a "satanic court'' the United Nations' Yugoslav war crimes tribunal trying his former political master Radovan Karadzic.
He made the comments at the start of his evidence on Tuesday in The Hague, Netherlands.
"I do not recognise this hate court," Mladic told the International Criminal Tribunal for the former Yugoslavia, nevertheless then taking the oath.
Mladic, known as the "Butcher of Bosnia" for his alleged role in the Srebrenica massacre, is giving evidence under subpoenas as a defence witness for Karadzic, the former Bosnian Serb president.
The Hague court reunited the two alleged chief architects of Serb atrocities during Bosnia's 1992-95 war, in which 100,000 people died.
Karadzic hopes that Mladic will tell the court that they did not agree or plan to expel Muslims or Croats from areas under Serb control.
Mladic initially refused to testify, telling Presiding Judge O-gon Kwon,"Your subpoenas, your platitudes, your false indictments, I do not care one bit about any of it.''
Both men are on trial separately for crimes including genocide, and both insist they are innocent.