At least 11 people have died and more than 30 have been wounded by bombs at mosques in Baghdad and in the province of Diyala.
The highest casualty toll occurred in Kanaan, Diyala, 75km north-east of Baghdad.
The bomb went off as Sunni worshippers were leaving Friday prayers at the Omar Bin Abdul-Aziz mosque.
A worshipper said some 250 worshippers were leaving the mosque when the bomb went off near the gate.
Provincial elections are due to be held on 20 April, the first since 2010.
The BBC reports more than 11 election candidates have been shot dead in recent weeks.