NATO troops clashed with their Afghan army allies and called in air strikes, killing four Afghan soldiers and wounding six, Afghan provincial officials said on Saturday. Shahedullah Shahed, spokesman for the governor of Wardak province southwest of Kabul, said foreign forces and Afghan troops were both conducting operations on Friday night in the province when they started shooting at each other. "Four army soldiers were killed and six wounded when a foreign forces air strike hit their post," he said. "We don't know why it happened, but it is deeply regrettable." He said the strike had targeted an Afghan Army outpost in the area that had been newly established. The NATO-led International Security Assistance Force confirmed that an "incident" had taken place between Western and Afghan security forces, but declined to give further details. "We are working with the Ministry of Defence to determine the facts of the incident," said U.S. Army Lieutenant Nico Melendez, a spokesman for the force.