KABUL, Afghanistan_Three American service members were killed and another was wounded Saturday when an Afghan soldier opened fire on them in the country's eastern Nangarhar province, U.S. officials said.
The attack occurred in the Achin district, where U.S. Army special operations forces have been fighting with Afghan military against Islamic State-affiliated militants.
The insider attack _ the second of its kind this year _happened in an active combat zone, keeping investigators from being able to go to the area, said Ismail Shinwari, a district governor in Achin.
It wasn't immediately clear if the shooting involved a jihadist sympathizer, a personal dispute or a cultural misunderstanding. But the Afghan Taliban claimed that one of its members had infiltrated Afghan forces, opened fire on U.S. troops and killed four in Nangarhar province, according to the private SITE Intelligence Group.
The shooter was killed immediately by other Afghan soldiers.
In March, an Afghan soldier was killed after he fired on U.S. forces at a base in Helmand province, wounding three Americans.
Since 2008, there have been more than 90 insider attacks in Afghanistan, with at least 150 foreign soldiers killed and 187 wounded, according to the Long War Journal blog.
Six U.S. service members now have been killed in Afghanistan this year. The three soldiers killed earlier this year died fighting an Islamic State affiliate in Nangarhar. All were members of U.S. Army special operations.
