Hizbullah sources confirmed the group was responsible for firing at a Lebanese military helicopter, killing a navigator and forcing the aircraft to make an emergency landing, Channel 1 reported Thursday night. The helicopter was attacked as it flew over a Hizbullah stronghold in southern Lebanon, earlier on Thursday. According to a statement released by the Lebanese army, the helicopter was on a training mission when it came under fire from "armed elements" and was forced down in the highlands of the Iqlim al-Tuffah province. The statement said 1st Lt. Samer Hanna was killed and that the aircraft was damaged. No other crew were hurt. Hizbullah did not release a formal statement on the shooting. The terrorist group has not clashed with the Lebanese military in recent years and their forces often coordinate their activities. It is likely, for example, that the army would have informed Hizbullah that one of its helicopters would be flying over the area. Thursday's incident occurred outside the zone of operations of UN peace-keepers near the border with Israel, a region also patrolled by Lebanese troops. A top Shi'ite cleric, Sheik Abdul-Amir Kabalan, urged the army to investigate swiftly and suggested that a collaborator with Israel may have fired on the aircraft. Lebanese military was investigating the incident, Channel 1 reported. The area where the incident took place is a predominantly Shi'ite Muslim region southeast of the southern port city of Sidon, far from Lebanon's sensitive Syrian and Israeli borders. It's a stronghold of Hizbullah, who is believed to have bases and concealed positions there.