Lebanon's Hezbollah turned over to the authorities on Friday one of its gunmen who shot at an army helicopter and killed its pilot, security sources said.

The incident occurred on Thursday over Iqlim al-Touffah region. The area is controlled by the powerful political and military group Hezbollah, which fought a 34-day war with Israel in 2006.

Lebanon's as-Safir newspaper reported that Hezbollah gunmen had targeted the aircraft because they thought it was Israeli. It said the helicopter had landed and taken off again in a training drill. Hezbollah gunmen in the area "thought that there was an Israeli landing attempt (under way) and opened fire in the direction of the helicopter, hitting it", it said.

Hezbollah said earlier in a statement that it would cooperate fully with an investigation into the matter. The group described what happened as a "very tragic and painful incident".

The army said on Thursday the helicopter had made a forced landing after it came under fire from "armed elements". It said the incident was under investigation.

The army deployed in the southern border region, along with a reinforced U.N. peacekeeping force, after Israel's war with Hezbollah guerrillas in 2006. The incident occurred north of a region where the U.N. peacekeepers have a mandate to operate.

Hezbollah's weapons are already a controversial issue in Lebanon and were at the heart of an 18-month political crisis that pushed the country to the brink of a new civil war.

The Iranian- and Syrian-backed group, whose military wing is far stronger than Lebanon's army, says it needs the weapons to defend the country from Israel. Hezbollah enjoys generally good ties with the army.

The policy statement of a new national unity government recognises Hezbollah's right to use all means possible to liberate Israeli-occupied land claimed by Lebanon.