Investigation conducted by the U.N. Interim Force in Lebanon (UNIFIL) showed that Ibrahim Rhayyel, 15, was shot dead by Israeli gunfire in Bastara, a Lebanese farm liberated in 2000 and located near the disputed Shabaa Farms.

"We investigated today and ... he was killed on the Lebanese side," said Milos Strugar, UNIFIL's senior adviser, on Thursday.

Meanwhile, the cabinet decided to file a complaint to the Security Council "to put an end to continued Israeli terrorism against Lebanon's sovereignty, citizens, security and stability."

Prime Minister Fouad Saniora criticized Israel, saying that its killing of the shepherd was a blatant assault on Lebanon's sovereignty.

"The martyr was shot dead while he was on Lebanese territory. He had not crossed the border toward the occupied land," said Saniora, who met with U.N. Secretary-General Kofi Annan's Personal Representative to Lebanon Geir Pedersen later in the day.

Pedersen condemned the shooting following his meeting with Saniora and called for calm and restraint along the withdrawal line with Israel. "Everyone knows how serious the situation is ... and we denounce this incident," he said.

UNIFIL is in contact with all parties to prevent any further escalation or violation of the Blue Line, a border demarcation between Lebanon and Israel that was drawn by the United Nations after the Israeli withdrawal in 2000.

On Wednesday, Hizbullah leader Sayyed Hassan Nasrallah warned the Jewish state that if the shepherd was found dead, his group would retaliate.

Nawaf Musawi, a Hizbullah official in charge of international affairs, said Israeli soldiers who killed Rhayyel had infiltrated Lebanese territory by at least 650 meters before shooting the young shepherd.

"The autopsy showed that Rhayyel was shot from about 50 meters' distance and his body was found 700 meters away from the border line on the Lebanese side," Musawi was quoted in The Daily Star as saying.

Security sources told As Safir newspaper that Israeli troops crossed the Blue Line and entered some 100 meters inside Lebanese territories to kill the boy.

The shepherd's body was found by his father, Youssef Rhayyel, Thursday morning less than 24 hours after his disappearance. UNIFIL troops helped in retrieving the corpse that was riddled with three bullets. Rhayyel was found near his sheep, also killed by Israeli gunfire.

He was laid to rest in the southern town of Shabaa Thursday. During his funeral his father called on Hizbullah to avenge his son's killing.

Earlier on Thursday, the Israeli army said that an armed man with binoculars was seen crossing the U.N.-demarcated border. When he opened fire, Israeli soldiers responded and apparently hit him, the army said.

The Shabaa Farms is a volatile region that has been the scene of occasional flare-ups between Hizbullah and Israel.(Naharnet-AP-AFP)