NATO and an Afghan official say a man wearing an Afghan army uniform has killed a U.S. service member and an American civilian in the capital Kabul.
A NATO statement Wednesday said another U.S. service member and two U.S. civilians were also wounded and were in a stable condition.
Dawlat Waziri, spokesman for the Afghan defense ministry, said the attack took place inside a military base.
The NATO statement said the attacker was later killed. The victims were conducting duties as part of the larger NATO mission to train and advise the Afghan security services. An investigation was being conducted to determine the exact circumstances of the incident, the NATO statement added.