UN judges tossed a defiant Ratko Mladic from his own war crimes hearing Monday, after the former Bosnian army chief shouted at them, defied their orders and refused to enter pleas for his 11 charges of masterminding atrocities during the Bosnian War.

Once guards removed Mladic from the room, presiding Judge Alphons Orie continued the hearing and formally entered not guilty pleas to 11 charges on Mladic's behalf, which is proper protocol for suspects who refuse to plead.

Shortly before security escorted Mladic from court, he shouted at Orie, "You want to impose my defence, what kind of a court are you?"

Mladic, 69, is charged with overseeing the worst Serb atrocities of Bosnia's 1992-95 war. The former Bosnian army chief is accused of genocide for his role as the top military official over seeing the 1995 killing of some 8,000 Muslim men and boys at Srebrenica, in Europe's worst mass killing since World War II.

Frank Chalk, Concordia University history professor, said he isn't surprised that the bombastic Mladic wouldn't sit still to listen to his charges.

"They involve major crimes against humanity and serious war crimes," Chalk told CTV's Canada AM.

"He comes from a military background and he's accused of the most serious crimes that a general can ever be accused of."

Monday's tribunal was Mladic's second appearance before the UN court since being extradicted by Serbia just over a month ago.

Despite Mladic's difficult behaviour, Chalk says the biggest challenge for prosecutors will be trying to prove the former army chief had genocidal intent -- a contentious matter in courtrooms.

"It will be hard to prove genocide and prosecutors often try to avoid the charge," he said. "But in this case it's clear that they have a lot of evidence."

But whether someone is charged with crimes against humanity or genocide, the end sentence is typically the same, Chalk said, explaining Mladic might receive life imprisonment for 30 years or more.

The former Bosnian army chief was argumentative from the start of his Monday hearing, at one point putting on a cap and interacting with members of the public much to Orie's chagrin.

Speaking out of turn, he told Orie he wanted to wear the cap because his head was cold.

Mladic had threatened to boycott the hearing because court officials have not yet appointed the Serbian and Russian lawyers he wants to represent him at his trial.

Orie told Mladic it was up to the court's registry, not judges, to approve the two attorneys.

When Orie asked Mladic whether he was ready to hear the charges, Mladic responded "You can do whatever you want."

But when Orie began speaking, Mladic said "No, no, no! Don't read it to me, not another word," and pulled off his earphones. After Orie warned him to be quiet or he would be removed, Mladic shot back: "Remove me."

After removing Mladic and entering the pleas, Orie adjourned the hearing without setting a date for trial or scheduling another hearing.

There is a possibility that Mladic's lawyers will be approved by the registry after filing proper papers, and then judges can set a date for the next pretrial hearing.

Orie told court-appointed lawyer Aleksander Aleksic that if he is able to communicate with Mladic, he should inform him of his not-guilty pleas and that he has the option of changing them at any time.

Mladic's courtroom antics came just a week before solemn commemorations in Srebrenica marking the 16th anniversary of the massacre.

Next Monday, 600 more bodies unearthed in the last year from mass graves in the hills surrounding the town and identified using DNA will be laid to rest at a cemetery for Srebrenica victims. Later this week, mourners will begin a three-day peace march through the Srebrenica woods where Muslim men and boys tried to flee the slaughter.

With files from The Associated Press