Three American soldiers were killed and one other was wounded after an Afghan soldier opened fire on them in eastern Afghanistan on Saturday, according to Afghan officials.
A statement by the United States Defense Department confirmed the death of the three Americans, and said the fourth had been evacuated for medical treatment. The statement said the military was investigating the episode.
Earlier, an American airstrike in southern Afghanistan accidentally killed at least two Afghan policemen, according to Afghan officials.
The incident in eastern Afghanistan occurred in the Achin District of Nangarhar Province, where American Special Operations forces are fighting alongside Afghan forces against Taliban insurgents and fighters aligned with the Islamic State.