Journalists saw Jean Jacques Ratsietison being taken away by the police.

The opposition has alleged that this month's election is being rigged in favour of the incumbent, Andry Rajoelina.

The electoral commission has not commented on the allegation.

Several recent attempts to stage demonstrations have been broken up by the police.

Political tension is high in Madagascar. Last month two candidates, including former President Marc Ravalomanana, were injured during opposition protests.