An attacker wearing an Afghan army uniform opened fire on international troops Sunday in southern Afghanistan, killing one, NATO said. Coalition forces returned fire and killed the attacker. The shooting was the latest in a string of attacks against U.S. and other foreign forces by their Afghan partners or assailants posing as them. The alliance did not provide more details, saying an investigation was under way. It also did not disclose the nationality of the service member killed. NATO usually waits for member nations to provide those details. Such attacks have raised the level of mistrust and ill will between the U.S.-led coalition and its Afghan counterparts and drawn concern about the readiness of government forces to take over their own security ahead of the 2014 deadline for the withdrawal of foreign combat troops. The insider threat to foreigners trying to mentor and strengthen Afghan security forces has existed for years but has grown more deadly. The U.S.-led coalition routinely reports each time an American or other foreign soldier is killed by an Afghan in uniform, but the military is under-reporting the number of overall attacks. The Associated Press reported earlier this month that the International Security Assistance Force, or ISAF, does not report attacks in which the Afghan wounds — or misses — his U.S. or allied target. It also doesn't report the wounding of troops who were attacked alongside those who were killed.