A Nato soldier in Afghanistan has been shot dead by a man wearing an Afghan army uniform, say officials.
The International Security Assistance Force (Isaf) said it was investigating the incident, which happened in the south of the country.
It is not yet clear whether the Afghan man was a genuine member of the army or an insurgent posing as a soldier.
The incident comes as Isaf prepares to hand over control of some security operations to Afghan troops.
The nationality of the dead man has not been disclosed.
In a statement, Isaf said that "an individual wearing an Afghan National Army uniform turned his weapon" against the troops.
A senior police detective told Reuters the shooting took place during a joint Isaf and Afghan army security patrol.
Some similar incidents were later been found to have been carried out by insurgent imposters.
The Afghan army has strict security screening procedures for its recruits, but there have been several incidents in which its personnel have fired on foreign soldiers.