Israeli soldiers clashed with Lebanese Hezbollah (search) guerrillas along the border Tuesday, leaving two soldiers and one guerrilla dead and prompting an Israeli general to threaten Hezbollah and its sponsors — Syria and Iran.

The renewed fighting, the most serious in months, followed a Beirut bombing Monday that killed a veteran Hezbollah commander. Hezbollah blamed Israel for the assassination, but the Israeli army denied involvement.

Israel and Hezbollah traded blame Tuesday over who precipitated the most serious fighting in months. Lebanon's government, meanwhile, complained to the U.N. Security Council (search) about the attacks, saying Israel violated Lebanese airspace, killed a Lebanese guerrilla fighter and caused material damage, a Foreign Ministry official said on condition of anonymity.

Unlike most of the previous clashes, Tuesday's incidents were far from the disputed Chebaa Farms, where Israel and Hezbollah frequently exchange gunfire.

The Israeli army said two soldiers died Tuesday and helicopter gunships attacked Hezbollah positions. Hezbollah confirmed one guerrilla was killed.

Witnesses in southern Lebanon said two Israeli helicopters fired two rockets at guerrillas near the border village of Aita Shaab, about nine miles southeast of coastal Tyre. Later, an Israeli helicopter staged a raid in the same area, security officials said.

The Lebanese security officials, speaking on condition of anonymity, said an Israeli tank fired on a Hezbollah position near Aita Shaab, killing one guerrilla.

Hezbollah returned fire across the border. Israeli helicopter gunships later fired back, the officials said.

A Hezbollah statement said the guerrilla was killed by Israeli tank shell targeting a Hezbollah observation post near Aita Shaab late Tuesday morning.

Israeli helicopters then attacked another observation post at nearby Ramia, but there were no casualties or damage, Hezbollah said.

The militant Shiite Muslim group vowed it would "choose the time and place for a deterrent response to make the enemy understand that aggression against the security and blood of our people would be very costly."

"The Zionist enemy is fully responsible for what happened and what is happening in Lebanon," Sheik Hassan Ezzeddine, Hezbollah's media chief, told The Associated Press.

"It (Israel) is the side that moved the battle out of its natural frame in Chebaa Farms."

In Israel, Maj. Jacob Dallal of the military spokesman's office said Hezbollah shot first at an Israeli border post and Israeli military action responded to the "provocation."

Later, Maj. Gen. Benny Gantz, the Israeli area commander, said the day was not "far away" when Israel would "act widely, severely."

"I don't believe Hezbollah will be the only address at that time. I think this is a matter of state responsibility, and these two countries (Syria and Iran) that host and direct financing and training Hezbollah organization will end up paying its price," Gantz said.

Syria and Iran support, sponsor and help arm Hezbollah, which is on the U.S. State Department's list of terrorist organizations and was largely responsible for pushing Israel to end its 18-year occupation of southern Lebanon in 2000.

Syria and Iran have long been Israel's enemies. Syria is the main power broker in Lebanon, and Israel charges that Syria could rein in Hezbollah if it wanted to.

Including Tuesday's deaths, 13 Israeli soldiers have been killed in cross-border confrontations since the withdrawal. Also, one Israeli civilian was killed by fire from Lebanon in October.

After the initial clashes, Israeli helicopters and tanks attacked Hezbollah positions in southern Lebanon and fighter jets shook the Lebanese capital with sonic booms. There was confusion over whether the three loud explosions that shook Beirut were airstrikes or just "mock raids" — warplanes making low runs and breaking the sound barrier.

A Palestinian guerrilla official first said jets targeted a base of the Popular Front for the Liberation of Palestine-General Command (search), a radical Syrian-based guerrilla group. However, he later said there was no raid and the sonic booms were mistaken for missiles.

Lebanese security officials also said there were "mock raids" over the hills of Naameh, five miles south of Beirut, an inaccessible area where guerrillas have an underground base. The area was targeted by Israeli jets last month.

Israeli military officials confirmed that planes flew over Lebanon but denied firing at targets.