An Israeli soldier was killed by a Lebanese army sniper late Sunday as he drove along the border, the Israeli military said, drawing Israeli threats of retaliation.
The shooting near Rosh Hanikra raised the possibility of renewed fighting in the volatile area, which has remained mostly quiet since a month-long war in the summer of 2006. Hezbollah, the guerrilla group that waged the war seven years ago, did not appear to be involved in Sunday's incident.
Lebanon's National News Agency confirmed the shooting by member of the Lebanese army. It was not clear why the soldiers opened fire. The Lebanese army has opened fire in the past after saying Israeli soldiers had tried to infiltrate. Lebanese security officials did not immediately comment.
Lt. Col. Peter Lerner, an Israeli army spokesman, said Israel had protested "this outrageous breach of Israel's sovereignty" with U.N. peacekeeping forces and heightened its state of preparedness.
"We will not tolerate aggression against the state of Israel, and maintain the right to exercise self-defense against perpetrators of attacks against Israel and its civilians," he said.
Since the 2006 war, the border has experienced only sporadic violence. Israel has responded with airstrikes and artillery fire following a number of rocket attacks and shootings across the border. In the most serious incident, a high-ranking Israeli officer was killed by a Lebanese sniper in 2010 after Israeli forces tried to cut down a tree along the border. Israel responded with artillery fire, killing two Lebanese soldiers and a journalist.
Andrea Tenenti, a spokesman for U.N. forces in southern Lebanon, said the U.N. was informed of a "serious incident" along the border. He said the peacekeeping force UNIFIL was in contact with both the Lebanese and Israeli armies, and that they were cooperating.
"The incident happened on the Israeli side of the blue line," he said, referring to a U.N.-drawn line demarcating the border between the two enemy states. He gave no further details, saying UNIFIL was still investigating.
The 2006 war broke out after Iranian-backed Hezbollah guerrillas crossed into Israel and captured two Israeli soldiers. The ensuing month-long conflict killed about 1,200 Lebanese and 160 Israelis.
Hezbollah, which has an arsenal of tens of thousands of missiles and rockets aimed at Israel, is preoccupied with the war in neighboring Syria, where it is aiding the forces of President Bashar Assad. Israeli officials believe Hezbollah is not interested in opening a new front with Israel at the current time.