Madagascar presidential hopeful Laza Razafiarison was arrested Tuesday after holding an unauthorised rally, the security forces said.
Razafiarison, who is considered an underdog in the country's upcoming presidential election, held a protest late Monday that police broke up with tear gas.
"We have arrested seven other people with Laza Razafiarison and they will likely appear in court tomorrow," gendarme commander Florens Rakotomahanina told AFP.
The presidential election -- meant to end a four-year political crisis -- has repeatedly been put on hold amid controversy over the candidacy of the three front runners.
Regional mediators have called for current ruler Andry Rajoelina, who seized power from Marc Ravalomanana in a 2009 coup, as well as Ravalomanana's wife Lalao and veteran leader Didier Ratsiraka to step back from the polls.
But all three candidates have refused.
The Indian Ocean island has been in political limbo since Rajoelina, a former disc jockey and ex-mayor of the capital Antananarivo, seized power.