Mladic repeatedly interrupted the proceedings of the International Tribunal for the Former Yugoslavia at The Hague, Netherlands, challenging the legitimacy of the tribunal, The New York Times reported.
"I'm not going to listen to this," Mladic told Judge Alphons Orie during an exchange about court's right to enter pleas on the defendant's behalf.
Mladic said he refused to enter pleas because he wasn't represented by lawyers of his choice. The court had appointed a lawyer to represent him but Mladic said he wants to be represented by two different lawyers, including one from Russia.
After several warnings to Mladic not interrupt, Orie said: "The court orders that you be removed from the courtroom."
"This is not a court," Mladic said. "Who are you? You are not allowing me to breathe."
Mladic was arrested in Serbia on May 26 after nearly 16 years on the run. The 69-year-old military commander was indicted in 1995 by the tribunal for genocide, war crimes and crimes against humanity. He is accused of being responsible for ethnic cleansing in Bosnia from 1992 to 1995, including the siege of Sarajevo, the Srebrenica massacre and the hostage-taking of U.N. personnel.
Returning from a recess, Orie returned and entered pleas of not guilty on Mladic's behalf.
The day's session began with Orie warning Mladic and the gallery that non-verbal communication would not be tolerated, Radio Netherlands Worldwide reported.