Israel has begun fortifying a fence along its volatile border with Lebanon, reinforcing an especially dangerous section that has been susceptible to sniper fire and other threats, military officials said Tuesday.

The military said the project was strengthening a one-kilometer (half-mile) section of an existing fence in Israeli territory, and no modifications to the route were being made. Even so, to avoid friction, it said construction was coordinated with the Lebanese army and the U.N. peacekeeping force in the area, UNIFIL.

Israel has no diplomatic relations with Lebanon. The two countries have been in a state of war for six decades.

The project is taking place near the spot where an Israeli officer was killed by a sniper two years ago. The shooting took place as the Israeli army was clearing brush that it said Lebanese guerrillas could use for cover. The new structure, near the town of Metulla, will include concrete sections about seven meters (20 feet) high, along with electronic sensors, officials said.

They spoke on condition of anonymity under military regulations.

In the Lebanese town of Kfar Kila, across the border from Metulla, an Israeli military patrol was visible on the Israeli side as Israeli work crews set up cement blocks in trenches along the border. Other Israeli vehicles could been seen on a hill overlooking the works.

On the Lebanese side, U.N. peacekeepers and Lebanese soldiers appeared to be on alert, with more vehicles and patrols than usual.

A senior Lebanese security official confirmed the construction had been coordinated through UNIFIL, which has served on the Lebanese side of the border since 1978.

"We have been informed of the start of the work yesterday, and the Lebanese army along the border is observing it," he said, speaking on condition of anonymity under army guidelines.

Construction began Monday and will take about 30 days.

The Israeli-Lebanon border is about 50 miles (80 kilometers) long and is already fortified with barbed wire and electronic sensors, a result of its decades-long history of violence. Militants repeatedly infiltrated into Israel and fired rockets in the 1970s and 1980s, triggering two wars.

In 2006, Hezbollah guerrillas burst across the border west of the section being rebuilt and captured two Israeli soldiers, sparking a monthlong war.

The border has been largely quiet since then, but there have been sporadic outbreaks of violence. Last year, pro-Palestinian activists in Lebanon attempted to burst across another part of the border into Israel, sparking clashes in which 10 people were killed, according to Lebanese officials.

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Associated Press writer Zeina Karam in Beirut contributed to this report.