Tuesday's assault appeared to be the latest in a string of insider attacks that have threatened to sever the partnership between international troops and the Afghan forces they are trying to train to take over responsibility for the country's security. There have also been cases of insurgents donning Afghan uniforms in assaults.
The NATO alliance does not give further details in its statement, saying the shooting is still under investigation.
At least 53 international troops have been killed in confirmed attacks by Afghan soldiers or police this year, and a number of other assaults are still under investigation.
