Baghdad (CNN) -- A string of attacks across central Iraq on Monday killed at least a dozen people and wounded more than 50 others.
At least seven people were killed and 20 others wounded when a bomb exploded inside a popular coffee shop in al-Taji, about 20 kilometers (12 miles) north of Baghdad on Monday morning, authorities said.
Taji is a predominantly Sunni district.
Separately, a roadside bomb exploded at a police patrol and killed two people and wounded three others in Thiraa Dijla, about 10 kilometers north of Baghdad, police told CNN.
And in Falluja, west of Baghdad, a suicide bomber wearing a police uniform walked into an election center and detonated an explosives-filled vest, killing three and wounding 30 others. Most of the dead were members of the Iraqi police.
The violence comes on a special voting day for security forces, police and others to cast votes ahead of provincial elections.
Security forces are on high alert.