Grenade blasts killed three people and injured 17 others in Burundi's capital, Bujumbura, which has been rocked by protests against President Pierre Nkurunziza's candidacy in June elections, police said Saturday. "Five unidentified people fired two grenades and shot several bullets at a police post" in northern Kamenge district late Friday, police spokesman Pierre Nkurikiye said at a press conference. According to dpa, the attack killed a senior police officer and another officer who were on night patrol, as well as a passer-by, and injured 12 people. A grenade was also fired at a police post near where the central market was formerly located, injuring five police officers, Nkurikiye said. Thirteen police officers were among the injured. Three of the victims were in serious condition. Police were investigating the attacks.