A man wearing an Afghan National Army uniform turned his gun on NATO soldiers in southern Afghanistan on Saturday, killing one service member, the U.S.-led coalition said.

The incident was the most recent in a string of attacks executed by men wearing Afghan army or police uniforms, creating tension between NATO troops and the Afghan recruits whom they are charged with training.

The attack took place outside the city of Lashkar Gah, the capital of Helmand province, according to the Associated Press. Lashkar Gah is one of seven areas where NATO is due to hand over control to Afghan security forces over the next two weeks.

Maj. Jason Waggoner, a spokesman for the International Security Assistance Force, said the incident was being investigated, adding, “There’s an ongoing Afghan-led search for the attacker, who is still at large.”

In April, an Afghan pilot opened fire on foreign troops at an air force training center in Kabul, killing eight U.S. service members and an American civilian contractor. In May, two U.S. soldiers in Helmand were killed by a man wearing an Afghan police uniform. Dozens more NATO troops have been killed or injured in similar attacks.

The Taliban has asserted responsibility for several such rogue shootings, but some have stemmed from friction between units, according to NATO officials.

NATO also reported the killings of two other service members — one in a roadside bombing Saturday in southern Afghanistan and another in an insurgent attack Friday in the west, the AP reported. The nationalities of the dead were not released.