Judges on Tuesday will decide if there is enough evidence to try him for masterminding a bloody election standoff two years ago, when four months of fighting left some 3,000 dead following his refusal to concede defeat to current president Alassane Outtara.

Prosecutors say Gbagbo, who faces four counts including murder and rape, spearheaded a plan to "stay in power by all means... through carefully planned, sustained and deadly attacks" against supporters of the election winner.

"Hundreds of civilian opponents were attacked, killed, wounded or victims of rape as a result of this policy," the prosecution said.

Gbagbo is the first former head of state to appear before the Hague-based court, where hearings will last just over a week.

Large-scale killings

Between November 28, 2010 and May 8, 2011 Gbagbo's forces killed between 706 and 1,059 people and raped more than 35 women, prosecutors say.

In one instance, some 80 people were massacred when perceived Ouattara supporters were attacked in the northwestern Abidjan suburb of Yopougon a day after Gbagbo's arrest by rival forces.

"The perpetrators were armed with Kalashnikovs and machetes. They attacked people in the street, sometimes stopping them at illegal roadblocks," prosecutors said, adding "victims were summarily executed or burnt alive, under the eyes of police officers who did not intervene."

In a reminder of tensions still simmering, the same neighbourhood of Yopougon on Saturday saw riot police fire tear gas to disperse a group of around 50 pro-Gbagbo supporters.

Ouattara's Interior Minister Hamed Bakayoko had banned the demonstration but youths nevertheless gathered, shouting "Free Gbagbo" and charging a police barrier.

Judges at the ICC said on Friday Gbagbo's mental health was fragile, but that he was fit enough to stand trial. Special measures including shorter sessions or letting the former president excuse himself and appear via video could be made possible, they said.

The hearings are expected to end on February 28, when Gbagbo is expected to make a statement.