Colonel Abdul Qadir al Harky, the head of police in Makhmour, said there were many bodies under the rubble and he expected the death toll to rise.
"The bomb hit area with several government offices," he said.
Other security sources said a KDP local meeting was in progress at the time of the attack.
It was the second suicide attack in Kurdish areas of the north in four days.
Makhmur is just south of the autonomous Kurdish-controlled areas, but it has a substantial Kurdish population.
The blast also killed the police chief and damaged the mayor's office, officials said.
The attack occurred four days after a truck bombing in Arbil, the capital of the Kurdish self-governing region, killed at least 15 people and wounding more than 100.