The radio station is critical of the Indian Ocean island’s strongmanAndry Rajoelina and two of its presenters were briefly detained earlier this month.
Free FM’s call for a protest drew between 3,000 and 5,000 people, according to an AFP reporter.
Despite appeals for calm by some of the organisers, the crowd soon headed for a downtown location known as “democracy square” where public gatherings have been banned.
“I’m here because there is a dictatorship, because we no longer have freedom of speech, no right to demonstrate,” one protestor who would not give his name told AFP.
The police then fired live bullets in the air and tear gas grenades to disperse the protest, the largest since social discontent started mounting around three weeks ago.
Saturday’s rally was not organised by any of the parties opposed to Rajoelina and police needed several hours to bring rioters under control.
On May 11, the South African Development Community had expressed concern over the deteriorating political climate in Madagascar and urged all players to refrain from escalation.
Rajoelina toppled president Marc Ravalomanana in March 2009 in an army-backed coup, plunging the impoverished country in a political and institutional crisis that has yet to be resolved.