The explosion and firebomb assaults appear linked to a campaign of stepped-up violence by militant factions in Bahrain, where majority Shiites have staged a nearly 30-month uprising calling for a greater political voice in the Sunni-ruled island.
Today's attacks also come on the eve of an emergency parliament session called to discuss the rising number of bombings, including one near Bahrain's royal palaces.
The Interior Ministry said three policemen were hurt in a bomb blast, and cars and buildings were hit by homemade firebombs.