A prison official says two guards who were wounded in a grenade attack during riots in Kenya's second largest city of Mombasa have died.

James Kodiany, the Coast regional prisons boss, confirmed that two of his officers died Wednesday. Another prison officer died on Tuesday after a grenade was thrown into a truck carrying security officers on their way to quell rioters that had set fire to a church. The death of the prison officers raised the death toll from two days of rioting following the killing of Muslim cleric Aboud Rogo Mohammed to four. A civilian was killed on Monday.

Mohammed, who was sanctioned by the U.S. and U.N. for his alleged support for an al-Qaida-linked militant group, was shot to Monday in his car.