NATO says at least one U.S. soldier was killed when a man wearing an Afghan army uniform opened fire on U.S. soldiers in eastern Afghanistan on Sunday.
The NATO-led coalition confirmed one soldier had been shot by a man in an Afghan uniform and that an investigation had been launched into the incident. 
According to a Reuters tally, Sunday's "insider attack" was the tenth such incident this year, and took the death toll of foreign personnel to 15.
104 Americans are among the total of 133 coalition soldiers killed so far this year in Afghanistan.