All the people killed were insurgents, according to Farid Mukhlis, the governor's spokesman.

Authorities said no NATO or Afghan troops, or civilians were killed in the clashes.

The attack took place at a military base in Barmal district, the spokesman said.

NATO's International Security Assistance Force said at least 30 insurgents were killed in the attack on the combat outpost. It was not clear why there was a discrepancy in the number of dead reported.

Five coalition troops were wounded during the battle, the force said in a statement.

"Insurgents attacked from all directions with rocket-propelled grenades, small arms and mortar fire," according to the statement, and a coalition air weapons team responded to the attack.