The agent from the National Directorate of Security (NDS) was in the Panjshir valley for personal reasons, when he got into an argument with some people from the NATO base, police chief General Qaseem Junglebagh told Reuters.

"He had a pistol, opened fire and killed two... He injured a third who opened fire and killed the NDS agent," Junglebagh said.

The NATO-led International Security Assistance Force (ISAF) confirmed one soldier and one civilian working for ISAF were killed in an attack on Saturday, but gave no further details.

Junglebagh had said both the dead were soldiers. Civilians working for the military in Afghanistan often wear body armor, and some have military-style uniforms. Provincial Reconstruction Team bases where many live are heavily fortified and frequently serve as both military and development hubs.

The deaths are the latest in a string of killings of foreign troops by Afghan security forces. Often NATO forces have been targeted by men they were mentoring or fighting beside.

The deputy governor of Panjshir, Abdul Rahman Kabiri, said the NDS agent worked in Kabul but was originally from Panjshir's Dara district, where the shooting took place.

Kabiri and Junglebagh said they had no details on the cause of the argument.

Panjshir and Bamiyan, which have long been peaceful anti-Taliban strongholds, are the only provinces that will be handed over in their entirety in the first phase of transition. Both are already largely in Afghan hands.