The police convoy was caught in a firefight in the remote province of Badakhshan on Wednesday when officers were returning from an anti-insurgent operation.

"The acting interior minister is deeply saddened about the killing of 18 policemen and wounding of 13 others in a terrorist attack in Warduj district of Badakhshan," a statement from the interior ministry said.

"A group of Afghan police forces on their return from a clean-up operation on the outskirts of Warduj district faced an enemy ambush and it resulted in the killing of brave Afghan policemen."

The mountainous northeast of Afghanistan is far from the Taliban heartlands of the south and is relatively peaceful.

But Taliban militants killed 17 captured Afghan soldiers in the same district in March. The men were taken hostage while guarding a convoy.

Afghanistan's 350,000-strong security forces are suffering a steep rise in casualties as the NATO combat mission winds down and Afghan authorities try to impose stability ahead of the presidential election due in April.

Last month 22 police were killed when hundreds of fighters ambushed a police and military convoy in the eastern province of Nangarhar.

The Afghan government declines to release exact figures, but the US department of defense has said that about 400 Afghan police officers and soldiers are killed every month in action.

The interior ministry said 47 insurgents were killed and 20 others were wounded in recent efforts to clean Warduj district of militants.

NJF/NJF