An insider attack has left at least three American troops dead and three others injured in Afghanistan’s eastern province of Paktika.The incident happened on Saturday when an Afghan soldier opened fire on the U. S. forces, a statement from the provincial governor ' s office said.The Afghan soldier was also killed in the shooting.There have been five insider attacks on foreign forces so far this year, with a total of eight troops and one U. S. contractor killed, AP reported.In another attack in Afghanistan’s western Farah Province, an Italian soldier was killed and three more soldiers wounded, the governor’s spokesman, Abdul Rahman Zahwandi, said.The attack occurred when the Italian soldiers were returning to their base after training Afghan security forces, the Defense Ministry said.The new casualties brought the number of U. S. - led forces killed in Afghanistan to 16 this month.Seven Georgian soldiers were killed in a bombing attack at their base in the south of Afghanistan on Thursday.