A man in an Afghan army uniform on August 5 fired at foreign troops in a military base, killing at least one person and injuring 14.
Germany's military said one NATO soldier was killed, while 14 NATO soldiers were wounded, including a German brigadier general, who was "not in a life-threatening condition."
Reports quoting unnamed U.S. officials said the dead NATO soldier was American.
An Afghan military official, General Mohammed Afzal Aman, said that "it appears that an Afghan army officer opened fire," adding that three Afghan officers were injured.
Aman said that "ISAF (International Security Assistance Force) troops have also suffered casualties."
NATO said it was investigating an "incident" involving both Afghan and international troops at Camp Qargha, a training base for Afghan forces to the west of Kabul.
Afghan President Hamid Karzai denounced the attack, describing it as "an act by the enemies who don’t want to see Afghanistan have strong institutions."
With additional reporting by AP and Reuters