Eighteen civilians, including children, were burnt alive when a helicopter gunship hit a convoy of families fleeing an offensive that has left the country almost cut off from the outside world and waking up each day to new scenes of devastation.

The operation was extended to bombing the lighthouse, radar installations and grain silos at the port in Beirut, the first attack by Israeli forces so close to the heart of the centre of the Lebanese capital.

With missiles also slamming into no-man's land between Lebanon and Syria, Russia warned that there was a "real threat" that the fiercest conflict between the two neighbours in a decade could engulf other nations.

"There is a real threat of the involvement of other states in this conflict," Russian Defence Minister Sergei Ivanov said ahead of a G8 summit of world leaders in Saint Petersburg likely to be dominated by crisis.

In an emotional televised address to the nation, Lebanese Prime Minister Fuad Siniora called for an immediate ceasefire and the end to the "collective punishment" of his country.

Splits have emerged within the international community, with some UN Security Council members rebuking Israel for "disproportionate" use of force but the United States insisting the Shiite Muslim group Hezbollah stop its attacks.

The crisis also prompted Arab League chief Amr Mussa to declare the Middle East peace process as "dead" after an emergency meeting of Arab foreign ministers over the Israeli offensives against Lebanon and Gaza.

Thirty-eight Lebanese civilians and one soldier were killed on Saturday, bringing to at least 100 the fatalities in Lebanon since the conflict erupted following the capture of two Israeli soldiers in a Hezbollah raid on Wednesday.

Eighteen civilians, including nine children, were burnt alive when missiles from an Israeli helicopter gunship slammed into a convoy of residents fleeing border villages in south Lebanon, UN and hospital sources said.

sraeli helicopters also fired two missiles at the port in the mainly Christian city of Juineh and in Tripoli while the military said it attacked the Beirut headquarters of Hamas, the first time the Palestinian militant group has been targeted in this offensive.

The four days of raids have left near-apocalyptic scenes of power stations burning, black smoke billowing from the paralysed airport, roads riddled with craters and collapsed bridges.

In another unprecedented action, an Israeli fighter bomber fired four missiles about 200 meters (yards) beyond Masnaa, the main crossing point between Lebanon and Syria, Lebanese police said.

However Damascus denied its territory had been hit and Israel's head of military operations General Gadi Azincot said later that Syria was "not an objective of our operation."

As a fresh barrage of guerrilla rockets rained on northern Israel -- including for the first time the Galilee town of Tiberias, Israel warned that Hezbollah could strike as far as the commercial capital Tel Aviv.

Four Israelis have been killed and scores wounded, sending tens of thousands of residents into bomb shelters or fortified rooms.

And the military said it had deployed a battery of anti-missile Patriot missiles in its third largest city of Haifa, which was hit by a Hezbollah rocket attack on Thursday.

Israel recovered the body of one of four sailors missing after what it said was an attack by an Iranian-made rocket on a ship patrolling off Lebanon on Friday, bringing to nine the number of servicemen killed since Wednesday. Iran denied any involvement.

Israel's onslaught was unleashed after Hezbollah guerrillas snatched two soldiers Wednesday, opening up a new battleground following a similar deadly offensive against Gaza over the capture of another soldier by Palestinian militants three weeks ago.

Lebanon remained virtually cut off from the outside world after Israel imposed an air and sea blockade, launched repeated strikes on its only international airport and bombed the main highway to Syria.

As foreign governments sought to evacuate stranded nationals, Beirut residents were stocking up on basic goods and making plans to flee to the relative safety of the mountains outside the capital.

Lebanon failed at an emergency UN Security Council debate Friday to secure a ceasefire to halt Israel's offensive, with the United States standing firmly behind its ally Israel.

"The best way to stop the violence is for Hezbollah to lay down its arms, to stop attacking" Israel, US President George W. Bush said, while adding that Syria must "exert influence" on Hezbollah.

But Prime Minister Recep Tayyip Erdogan of Turkey, a key US ally and Israel's main Muslim ally, did not mince words criticising the Israeli offensive and the reaction of the international community.

"Bombs are exploding, innocent people are being killed, infrastructures are being destroyed... The powerful continue to crush the weak, but unfortunately those who hold the power in the world are keeping mum."

Lebanon has been mired in its own political crisis since the murder of ex-premier Rafiq Hariri in 2005 and is still rebuilding after the devastating 1975-1990 civil war.

Israel also pressed on with its air assault on Gaza on Saturday, killing two Palestinians in helicopter strikes after the United States on Thursday vetoed a UN resolution calling on Israel to halt its military operations there.

At least 78 Palestinians and one Israeli soldier have been killed since Israel launched its assault on Gaza, which the United Nations has warned is causing a humanitarian crisis in one of the most densely populated areas on earth.

Both Hezbollah and Palestinian militants holding the soldiers are demanding the release of prisoners from Israeli jails -- something Israel has rejected outright.