Bujumbura - At least three people were wounded when a grenade exploded in the centre of the Burundian capital Bujumbura on Thursday, witnesses said, the latest in weeks of unrest ahead of elections.
"Three of my colleagues were injured, one of them seriously, his left arm was badly hurt," one builder told AFP, adding that he himself had escaped injury "miraculously".
A police officer at the scene said no suspect had been arrested.
Also read: Explosion shakes Burundi capital, deadly protests
Grenade blasts have become frequent events in Burundi in recent weeks.
The troubled central African nation has been in crisis since late April over President Pierre Nkurunziza's controversial bid to stand for a third consecutive five-year term, a move branded by opponents as unconstitutional and a violation of a 2006 peace deal that ended 13 years of civil war.
Parliamentary elections are planned for June 29, ahead of the presidential vote on July 15.
Police routinely accuse anti-government protesters campaigning against a third term for Nkurunziza for the attacks, while the protest leaders blame security forces "seeking a pretext to justify their excessive use of force and live ammunition. "