A suicide car bomber and gunmen wearing police uniforms killed at least 33 people here in the Iraqi city of Kirkuk on Sunday morning.
The huge car bomb was detonated in front of Kirkuk's police headquarters and next to the city's telephone exchange, killing more than 30 and wounding over 70 others.
Police said at least two gunmen were also involved in the assault.
This is the third major attack in the past few weeks in or near the city - an ethnically-mixed area of Arabs, Kurds and Turkmen at the heart of a dispute over oil and land between Baghdad's central government and the autonomous Kurdistan region.
Several armed groups are active in Kirkuk, and Sunni Islamist insurgents tied to al Qaeda often attack security forces in an attempt to undermine Shi'ite Prime Minister Nuri al-Maliki's government and stoke sectarian tensions.