Ivory Coast's former first lady Simone Gbagbo and the judge trying her for crimes against humanity clashed Tuesday, with military police forced to prevent her from leaving the courtroom.

"Where are you going? Stop her" the court president Boiqui Kouadjo told gendarmes as Gbagbo left the witness box to follow her lawyer who exited the Abidjan courtroom in protest against the proceedings.

Gbagbo refused to sit down.

"Condemn me if you want, but I'm tired of this. It's nonsense," she said before being admonished by the judge for talking to him "in that tone".

Simone Gbagbo is the wife of former Ivory Coast president Laurent Gbagbo, who was forced from power in 2011 by current incumbent Alassane Ouattara, who had won presidential elections five months previously -- the results of which his predecessor rejected.

She is also accused of being a member of a "crisis cell" that allegedly coordinated attacks by the armed forces and militias in support of Gbagbo.

She is already serving a 20-year sentence for "endangering state security".

Tuesday's exchanges began after the court rejected a defence request for high-profile witnesses to be called, including parliament's speaker, a former prime minister and a former army chief.

The trial had resumed Monday after being suspended for two weeks.

The court is scheduled to sit again on Wednesday but it was unclear whether the defence team would return to the proceedings.