Several coalition and Afghan troops were killed Monday when a person wearing an Afghan service uniform died on the group, NATO said.
Maj. Adam Wojack, a spokesman for NATO's International Security Assistance Force, said the attack occurred in eastern Afghanistan, CNN reported.
Officials told the BBC the shooter either was a local police officer or an insurgent posing as one.
The incident would be the latest so-called "green-on-blue" attacks, or attacks against coalition members by people wearing Afghan police or army uniforms.
On Friday, a coalition contractor was killed when people in Afghan National Army uniforms fired on ISAF members, NATO said.