The rebels encircled the police station at Salman Pak and opened fire with anti-tank rockets and light arms, police said.

Military spokesman Lieutenant Colonel James Hutton said six policemen were killed and eight others wounded in the battle. He said an unknown number of insurgents were also killed.

An official at Kindi hospital in Baghdad said earlier that 42 police were wounded in the clashes and two had died in hospital.

"The insurgents did assume control of the police station temporarily," Hutton told AFP. "We attacked them with helicopters, which fired missiles, and the insurgents fled. The operation to pursue them is still going on."

American troops evacuated the wounded for treatment, said a US military statement, adding that "nearly 20 cars were on fire following the attack".

Iraqi national security advisor Qassem Daoud told AFP that "a military operation is going on against a terrorist group which has been in the area for two weeks".

Police special forces were taking part in the operation, he said.

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