NATO troops killed several people in northern Afghanistan overnight, giving rise to conflicting accounts of whether they were insurgents or civilians, officials said Tuesday.

The incident came as international troops raided a house in the relatively peaceful northern Afghan province of Sari Pul late Monday.

The provincial governor, Sayed Anwar Rahmati, told AFP the raid had killed six civilians.

"Foreign troops stormed a house in Sayyad district last night, killing six civilians and detaining four others," he said.

The deputy police chief for the province, Sayed Jahangir, confirmed the incident but said there was no proof the men were civilians.

The NATO-led International Security Assistance Force (ISAF) said they had killed five armed men.

"Afghan and coalition forces were engaged by five armed individuals during an operation last night," ISAF spokesman Major Tim James told AFP. "The Afghan and coalition forces returned fire, killing all five."

The killing of civilians by the US-led NATO force during military operations is an increasingly controversial issue fuelling Afghan opposition to the near 10-year military campaign to put down a Taliban insurgency.