An Afghan soldier turned his gun on US troops at a checkpoint on Saturday in the country's east, killing two Americans and at least two members of Afghanistan's army.
The shooting marked both the continuance of a disturbing trend of insider attacks and the 2,000th American death in the long-running war.
The shooting was at an Afghan army checkpoint just outside a joint US-Afghan base in Wardak province. An Afghan official said three Afghan soldiers were killed in the clash. It was not clear if the assailant was among the dead.