Concerns of a descent into full-blown conflict have been mounting in recent months as Iraq's delicate inter-communal balance comes under growing strain from the civil war in neighbouring Syria, where mainly Sunni rebels are fighting to overthrow a leader backed by Shi'ite Iran.
More than 1,000 people were killed in militant attacks in Iraq in May, according to the United Nations, the highest monthly toll since the sectarian bloodletting of 2006-2007.
In Taji, 20km (12 miles) north of Baghdad, a bomb exploded in a restaurant killing seven and a bomb attached to a minibus killed two people and wounded seven, police said.
A suicide bomber dressed in police uniform blew himself up at the entrance to a police headquarters in the city of Fallujah in the western province of Anbar, where police were gathering to cast their votes in provincial elections. Three people were killed.
Provincial elections in most of Iraq were held in April but the Shi'ite-led government delayed voting in the Sunni-dominated governorates of Anbar and Nineveh citing unrest. The election is due to be held on June 20.
© Thomson Reuters 2013