Two U.S. soldiers have been killed and another two wounded in an attack by an Afghan soldier, an Afghan official said Saturday. Attahullah Khogyani, spokesman for the provincial governor in Nangarhar province, said an Afghan army soldier opened fire on U.S. troops in an attack in the Achin district. No further details were provided on the extent of the injuries of the two wounded soldiers. The Afghan soldier has also been killed, Khogyani said. The U.S. military has yet to comment on the situation.