Three bombs targeting security forces in the northern Iraqi city of Kirkuk have left at least 27 people dead and injured dozens more, officials say.
Two of the bombs exploded in quick succession near a police station.
Many of the casualties were police officers who rushed outside after the first bomb went off.
One official blamed al-Qaeda for the attack. Kirkuk, about 180 miles (290km) north of Baghdad, has seen violence linked to ethnic divisions in the past.
Thursday morning's attacks were the most deadly the city has seen for some months.
The first explosion was caused by a small bomb in the police station car park, witnesses said.
"I ran out from the headquarters after I heard the first bomb. I went with my colleague to check the parking lot but as we arrived, a huge bomb went off," policeman Sherzad Kamil told AFP news agency.
"I fell on the ground and saw several of my colleagues killed and wounded."
About an hour after the explosions near the police station, a third blast nearby was reported to have targeted the convoy of a senior police official, injuring him and a number of officers.
The bombs badly damaged buildings, and charred cars could be seen flipped on to their roofs.
Overall, at least 70 people were wounded, officials said.
The police chief of Kirkuk province, Maj Gen Jamal Tahir, said the bombings bore the hallmarks of an al-Qaeda attack.
"It is a joint operation between al-Qaeda and the armed groups allied with them," he said.
Kirkuk lies in an oil-rich and ethnically divided area where Kurdish authorities are vying for control with the central government in Baghdad.
The city is populated by Kurds, Arabs and Turkomen.
US forces, who are due to withdraw from Iraq later this year, have been conducting tripartite patrols in Kirkuk with central government forces and Kurdish authorities.
While violence has decreased in Iraq in the last few years, attacks are still frequent and government or security officials are often targets.