NATO says two service members have been killed by men wearing Afghan National Security Forces uniforms in southern Afghanistan.
A NATO statement said the attack took place early on August 26 in Helmand Province.
The alliance said the attackers opened fire on the soldiers' vehicle inside the military compound. It said both shooters were killed when NATO forces returned fire.
The nationality of the victims was not disclosed.
So-called "green-on-blue" attacks -- when Afghan soldiers or police turn their guns on international troops -- have been a major problem during NATO's many years of fighting alongside Afghan forces.
The Helmand attack was the first such incident since April.
The Taliban did not immediately claim responsibility for the attack. Western officials say that most such attacks stem from personal grudges and cultural misunderstandings rather than insurgent plots.
The killings have bred mistrust among local and foreign forces, though fewer incidents have occurred in recent years.
Most NATO combat troops pulled out of Afghanistan last year but a small contingent remains, including roughly 10,000 American soldiers.