Burundian police say at least eight people have been wounded in a series of grenade attacks in the center of the capital Bujumbura.

Police spokesman Pierre Nkurikiye said two people have been arrested for their alleged roles in the attacks.

The first grenade exploded around noon Wednesday in front of a telecom shop operated by Vietnamese businessmen. Another explosion happened in the parking lot for the National Post Office headquarters, damaging an empty car. A third bomb exploded in Bujumbura's open market.

Bujumbura has been wracked by violence since April 2015 when President Pierre Nkurunziza announced he would seek a third term.

More than 400 people have been killed in the unrest, according to the U.N.