UNIFIL's senior adviser Milos Strugar told The Daily Star that a UNIFIL investigation into the incident had "confirmed the shepherd was killed inside Lebanese territories."

"The results will be communicated to the proper UN authorities," he added. Struger also said that a shotgun was found near the body of the dead boy.

"This is a blatant assault against Lebanon's sovereignty," Lebanese Prime Minister Fouad Siniora told Parliament, adding that Lebanon was in contact with the UN over the incident.

"The martyr was shot dead while he was on Lebanese territories, he had not crossed the borders toward the occupied land," said Siniora, who met with UN representative in Lebanon Gere Pedersen later in the day.

Pedersen condemned the shooting following his meeting with Siniora, calling on the concerned parties to practice "self restraint."

"Everyone knows how serious the situation is ... and we denounce this incident," he added.

The body of the 15-year-old shepherd, Ibrahim Rahil, was found early Thursday morning in the disputed Shebaa Farms area, less than 24 hours after his disappearance.

This incident threatens an escalation of tension along the already volatile border area.

The UN Secretary General Kofi Annan's spokesperson Stephane Dujjaric said: "The UN cannot comment on the incident until they have received a formal copy of the investigations. As far as we are concerned, the investigations are ongoing."

Israeli Army sources claimed during the day that Rahil was shot because he had crossed the UN-demarcated Blue Line toward the Israeli borders.

An army spokeswoman said an Israeli patrol had "spotted an armed man who crossed the international border line ... He fired at the troops who then returned fire and identified a hit."

However, Hizbullah foreign affairs official, Sayyed Nawaf Musawi said the killing was a deliberate breach of Lebanese sovereignty, and added that the Israeli soldiers who killed Rahil had infiltrated Lebanese territories by at least 650 meters before shooting the young shepherd.

"The autopsy showed that Rahil was shot from about 50 meters' distance, and his body was found 700 meters away from border line on the Lebanese side," Musawi said.

"This is a very blatant breach. It is not only the fact that Israeli forces killed a Lebanese civilian boy in cold blood, they also did it in the depths of the Lebanese territories," he added.

Musawi also denounced Israeli claims the boy was carrying a weapon.

"What is it to them? He was 700 meters inside Lebanese territories," Musawi said. "If that's the case, and they want to establish a new 'blood rule' of shooting everyone near the borders with weapons, we will shoot all their soldiers and all settlers who come near the border area with any sort of weapons, and everyone knows they are as close as five meters from the border line," he added.

Musawi also slammed the UN, saying that Hizbullah, as well as most of the Lebanese people, did not trust the international body to take action against Israel.

"We don't even expect them to denounce the incident," he said. "We know how to take our rights with our own hands."

Musawi said the resistance's response to the breach will come at the right time, with the proper response.

"Sayyed Hassan Nasrallah put it very clearly yesterday when he vowed to properly retaliate if the missing boy turned out to be dead as a result of Israeli fire, and I don't have anything to add to this."

Nasrallah, Hizbullah's secretary general, had warned Wednesday night that there would be harsh retaliation in the event that Rahil turned out to be dead as a result of Israeli fire.

Druze MP Anwar Khalil said following a meeting with Nasrallah Thursday that the attitude of all residents of the Lebanese South was to "support the resistance in its work."

"The Israeli enemy had asserted once again yesterday that it will not stop its breaches and assaults on the Lebanese, and the result yesterday was the killing of an innocent shepherd in the area," he said. "This is a clear sign that the assaults have not, and will not, stop."

The area of Shebaa Farms has been controversial since Israeli forces withdrew from the Lebanese South in 2000. Hizbullah, backed by the Lebanese government, asserts the area is Lebanese, while Israel and the UN say it is occupied Syrian land.

In November, clashes in Shebaa Farms left four Hizbullah fighters dead and 11 Israeli soldiers wounded. The most recent flare-up in cross-border violence was in late December when rockets fired from Lebanon crashed in the northern Israeli town of Kiryat Shmona, damaging property but causing no casualties. Israel retaliated with an air strike against a Palestinian military base south of Beirut.