The Afghan casualties were “a result of the engagement” on Saturday night, an International Security Assistance Force spokesman told AFP, but could not confirm whether they had been killed by the insider or in return fire by ISAF troops.
No further details of the incident were immediately available but a joint assessment of the incident by ISAF and the Afghanistan National Army was under way, the spokesman said.
The latest death takes the total number of ISAF troops killed in 36 insider attacks this year to 52, accounting for about 15 percent of all coalition casualties in the war.
NATO attributes about 20 percent of the attacks to infiltration by Taliban insurgents into Afghan security forces while the rest are believed to result from cultural differences and personal animosities between the allies.
The so-called green-on-blue attacks pose a serious threat to the NATO war effort, which has portrayed the advising and training of Afghan forces as the key to the scheduled pullout of Western troops.
Earlier this month, ISAF announced a scaling back of joint operations with its Afghan partners following a dramatic rise in the assaults, in which Afghan soldiers turn their weapons on their Western allies.
But US Defence Secretary Leon Panetta said on Thursday that troops had resumed most joint operations with Afghan forces.
Panetta vowed that the insider threat would not derail plans to transfer security to Afghan forces by the end of 2014, paving the way for the withdrawal of most NATO combat forces.
“We must and we will take whatever steps are necessary to protect our forces. But I also want to underscore that we remain fully committed to our strategy of transitioning to Afghan security control,” he said.