In Kirkuk, an oil-rich city in the north of the country, a truck bomb killed 10 people, including four policemen, at the al-Kuriya police station on Tuesday.
Forty-two people were wounded in the attack. Rescuers are still searching for bodies.
Kirkuk is just outside the borders of the largely autonomous Kurdistan region and its population is a volatile mix of Kurds, Turkmen and Sunni and Shia Arabs.
Iraq's security forces are regularly
targeted in Kirkuk [AFP]
A police source said many buildings in the area were severely damaged by the blast.
One resident said he saw many casualties in the street and several buildings had collapsed.
Iraqi security forces are frequently targeted by bombers seeking to undermine the US-backed Iraqi government.
Police in many areas of Kirkuk have also been infiltrated by militias, making them a target for rival armed groups.
Also on Wednesday, dozens of students demonstrated against twin bombings a day earlier at Baghdad's Mustansiriya university, which killed 70 people and wounded nearly 140.
Three days of mourning have been declared by the education ministry.
In all, at least 105 people were killed in bombings on Tuesday and a shooting in the capital on a day when the UN said more than 34,000 Iraqi civilians died in violence last year.
The UN said data from hospitals and mortuaries put the total civilian death toll for 2006 at 34,452.