The chief judge ejected Saddam Hussein from the court trying the former president and six co-defendants over the Anfal campaign against ethnic Kurds in the late 1980s.
Judge Mohammed al-Ureybi, who later announced a closed session, ordered Saddam to leave the courtroom after cutting off his microphone when he began talking after the first Kurdish witness finished giving testimony.
Other defendants immediately protested against the decision and began shouting at the judge. The judge then ordered out defendant Hussein Rasheed who called the prosecutors "pimps" and "traitors".
Rasheed punched one of the guards escorting him out.
It was the fourth time in the last five sessions that Saddam has been ejected since Mr Ureybi took over as chief judge.
Saddam (69); his cousin, Ali Hassan al-Majeed; and five former commanders face charges of war crimes and crimes against humanity for their role in Anfal (spoils of war) campaign that prosecutors say left 182,000 ethnic Kurds dead or missing.