Chad's former President Hissene Habre has been removed from the courtroom at his trial for crimes against humanity.
He shouted that the process was "a farce", as he was waiting for proceedings to begin.
The trial in Senegal's capital, Dakar, marks the first time one African country has prosecuted the former leader of another.
Mr Habre denies being responsible for hundreds of deaths during his rule from 1982 to 1990.
The trial follows a 25-year campaign to bring him to justice.
Many of Mr Habre's alleged victims have been calling for it since his overthrow and exile in Senegal in 1990.
Parallels were later drawn with the attempts to get the former Chilean military leader Augusto Pinochet extradited and put on trial for crimes against humanity in Spain in 1998.
Mr Habre does not recognise the court and was brought there by prison guards.
Waiting for the trial to open, the former Chadian leader shouted: "Down with imperialists. [The trial] is a farce by rotten Senegalese politicians. African traitors. Valet of America".
Mr Habre was taken out of the courtroom and the trial began without him.
He then refused to come in after the break that followed the opening statements, and the trial has been suspended until Tuesday when the judges ordered that Mr Habre would be forced to attend.
'Opportunity for Africa' - Laeila Adjovi, BBC Africa, Dakar
Victims of Hissene Habre's regime have waited 25 years to have this day in court.
Many doubted that Mr Habre would even show up, as up to now he had refused to cooperate with the court, but he did appear, albeit briefly, surrounded by a dozen security guards.
Despite the scuffle that took place inside the court-room as he was removed, the trial started on time and the first 100 witnesses are in Dakar waiting to give evidence.
The African Union requested that Senegal establish this court so that Mr Habre would be tried "on behalf of Africa".
As many see the International Criminal Court as unfairly pursuing African leaders, this trial is a step towards creating grounds for credible international justice in Africa.
This is a huge opportunity to show that Africa can hold its leaders to account.
At the end of his opening statement, prosecutor Mbacke Fall said that Mr Habre's "silence will not be seen as a defence strategy" and will not affect a fair trial.
Also addressing the court, victims' lawyer Jacqueline Moudeina said that the trial "is in the name of humanity, a humanity which Hissene Habre never allowed his victims".
Many of his alleged victims have been calling for the trial since his overthrow and exile in Senegal in 1990.
A Chadian truth commission found in 1992 that the Habre regime was responsible for 40,000 deaths and disappearances.
In 2005 a court in Belgium issued a warrant for his arrest, claiming universal jurisdiction but, after Senegal referred the issue to the African Union, the AU asked Senegal to try Mr Habre "on behalf of Africa".
Progress has been slow, as Senegal's previous President Abdoulaye Wade appeared to be reluctant to put him on trial.
He first said the country lacked funding and then, apparently fed up with the process, suggested that Mr Habre should be sent back to Chad where he had already been sentenced to death.
President Macky Sall, elected in 2012, agreed to a trial in a special tribunal set up within the Senegalese court system, and in 2013 the African Extraordinary Chambers was established with AU backing.
The court was set up to deal with crimes committed in Chad between 1982 and 1990.
Mr Habre was indicted in 2013 but he refused to cooperate with the special court.