DAKAR, Senegal -- Security officers dragged former Chadian dictator Hissene Habre into the courtroom Monday after he refused to take part in his trial on war crimes charges, and some of his supporters had to be removed after they charged to the front of the court.

Habre, 72, who is being tried here in Senegal as part of a special court designed to hold African leaders accountable on the continent, has denounced his trial as being politically motivated and has refused to participate.

On Monday, it took four security guards at one point to hold him down. He tried to thrash about as witnesses' names and a summation of the charges against him were read aloud. At one point, Habre began humming in his seat though he calmed down after about 20 minutes.

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The former Chadian leader lived comfortably for more than two decades in exile in Senegal's capital until he was arrested in 2013 and ordered to go before a special court. His government is accused of being responsible for some 40,000 deaths during his eight-year rule which ended in 1990, according to a truth commission report.

He faces charges of crimes against humanity, war crimes and torture, and could be imprisoned for up to 40 years if convicted.

The trial re-started on Monday after a suspension in July to allow the Senegalese lawyers appointed for Habre to prepare his defense after he refused representation.

On July 20, the first day of his trial, he cried out in court: "This is not a trial, this is a masquerade!" raising his fist as he was lifted and taken out of the courtroom by security guards. He refused to return that day.