As many as 100 attackers, armed with assault rifles, rocket-propelled grenades and mortars, took part in the raid, which began around dawn.The gunmen arrived in civilian vehicles and attacked the government compound in the centre of town, which included the police headquarters, a court house and city council building.
Police said the suspected insurgents detonated a string of roadside bombs as they escaped, one of which appears to have killed two other police officers rushing to the scene.
One report quoting police said the investigations were being hampered because the gunmen had seized radio equipment rendering the police network insecure.
The town's mayor, Alewi Farhan, said the attackers bombed access roads to prevent reinforcements coming to the aid of police.
"The insurgents pulled off a very well-planned attack," he said.
