Two NATO soldiers killed by gunman wearing Afghan uniform at Helmand military base

KABUL, Afghanistan, Aug. 26 (UPI) -- Two NATO soldiers were killed by gunmen who were wearing Afghan military uniforms on Wednesday in a base in the southern province of Helmand.

Soldiers on the base killed the gunmen when returning fire. The nationalities of the dead NATO soldiers have not been released.

This is the second "green-on-blue attack" this year, which are assaults on foreign troops by members of the Afghan security forces or a gunman wearing an Afghan military uniform acting individually or as part of an organization.

More than 100 foreign soldiers in Afghanistan have been killed in such attacks. No group has claimed responsibility for the recent attack. There are about 13,000 members of the U.S.-led coalition force in Afghanistan with the majority training, advising Afghan troops and providing security.

On April 8, a U.S. service member was killed and seven others were injured after an Afghan National army soldier opened fire following a meeting by U.S. and NATO officials.

The shootout occurred in the city of Jalalabad after officials met with the governor of the Nangarhar Province. One Afghan soldier was killed and another was injured when U.S. troops returned fire, but it is unclear if the Afghan soldier who opened fire was among them.