ADEISSEH, Lebanon — Lebanese and Israeli troops exchanged fire Tuesday in a fierce border battle that killed a senior Israeli officer, two Lebanese soldiers and a journalist – underlining how easily tensions can re-ignite along the frontier where Israel and Hezbollah fought a war four years ago.

It was the worst fighting since 2006 in the area, where Israeli and Lebanese soldiers patrol within shouting distance of each other, separated by the U.N.-drawn Blue Line boundary.

The fighting flared into Israeli tank, helicopter and artillery strikes near this Lebanese town, but ended after several hours and there was no sign that either side was preparing to escalate.

The Shiite guerrilla force Hezbollah said it offered to help the Lebanese army but in the end did not get involved. “We told our brothers, control yourselves and don’t do anything,” Hezbollah leader Sheik Hassan Nasrallah in a televised speech.

But, he warned, his fighters would intervene if Israeli troops ever attack Lebanese forces again. “Any Israeli arm extended against the Lebanese military will be cut off by the resistance,” said Nasrallah, whose arsenal is far more powerful than the Lebanese army’s.

The U.N. Security Council urged “utmost restraint.” U.S. State Department spokesman P.J. Crowley said, “The last thing that we want to see is this incident expand into something more significant.”

Tuesday’s clashes began after an Israeli soldier tried to remove a tree along the border, something the military has done in the past to improve its sightlines into Lebanon.

But both sides claimed the tree was in its territory. An Associated Press photo shows an Israeli standing on a crane reaching over the fence that Israel erected to separate the two countries. The fence, however, does not match the Blue Line in all places, and the Israeli military said in a statement that the tree was in Israeli territory.

The Lebanese military said the Israelis crossed onto Lebanese soil despite calls from the U.N. and Lebanon to stop. When the Israelis persisted, Lebanese troops opened fire with small arms and rocket-propelled grenades, it said in a statement.

The Israeli forces responded with “machine guns and tank shells, targeting Lebanese army positions and civilian homes in the area,” the Lebanese military said.

Israel, however, accused Lebanon of provoking the fight. Maj. Gen. Gadi Eizenkot, said that while soldiers were removing bushes by the fence, Lebanese military snipers shot two officers. A lieutenant colonel was killed.