The NATO-led International Security Assistance Force (ISAF) says two men in Afghan National Army uniforms shot dead two alliance soldiers in eastern Afghanistan.
ISAF did not reveal the nationalities of the foreign soldiers.
It said more information would be released later after an investigation into what happened.
An unnamed Afghan Interior Ministry official was quoted as saying the February 12 shooting took place in Kapisa Province, just north of Kabul.
There has been no claim of responsibility yet.
It was believed to be the first "insider" attack this year. Insider attacks in the past have been claimed by the Taliban.
According to a Reuters tally, there were 10 such incidents, resulting in the deaths of 15 ISAF soldiers, last year.
Based on reporting by Reuters and AFP