The head of the provincial council, Muhammad al-Musawi, said at least 150 people were wounded when two suicide bombers detonated their vehicles packed with explosives.
Earlier, a suicide bomber blew up his vehicle outside the Diyala province police command in the provincial capital of Baquba, 60 kilometers northeast of Baghdad, killing at least three people.
It was the third such strike on security forces in as many days.
The attack occurred a few blocks from a similar blast on January 19 in which a suicide attacker drove a bomb-packed ambulance into the headquarters of an Iraqi guard force, killing at least seven people and injuring nearly 70 others.
Earlier this week, a suicide bombing in Tikrit killed 65 people in a crowd of police recruits.