Israeli jets have launched fresh attacks on Lebanon as troops battled Hezbollah fighters in the south.
Many of those stranded in Tyre are poor and elderly
At least 17 civilians have been killed in the latest raids, which hit southern Beirut and parts of the east and south, cutting off the city of Tyre.
An Israeli soldier has been killed in the southern town of Bint Jbeil, while Hezbollah fired more rockets at Israel.
The action comes a day after at least 15 people were killed in Israel in its deadliest day so far of the conflict.
Diplomats are battling to find a workable truce amid the escalating violence.
UN diplomats are due to meet again in New York to try to overcome Lebanese opposition to the text of a ceasefire, while Arab ministers are discussing a strategy on the truce in Beirut.
More than 900 Lebanese, most of them civilians, have been killed in the conflict, the Lebanese government says. More than 90 Israelis, most of them soldiers, have also been killed.
Humanitarian groups say Israeli military action is hampering efforts to help many of the hundreds of thousands who have fled the fighting - sparked by the capture of two Israeli soldiers by Hezbollah on 12 July.
Officials have warned that an oil spill seeping from a Lebanese power station bombed three weeks ago threatens to pollute countries in the eastern Mediterranean.
A series of loud bangs woke Beirut residents at dawn as jets pounded the southern suburbs - a Hezbollah stronghold that Israel has regularly targeted.
Witnesses also reported air strikes in and around Baalbek in the Bekaa valley, while warplanes bombarded southern Lebanon throughout the morning.
The air attacks came amid further clashes on the ground.
The Israeli army said one of its soldiers and five Hezbollah militants died in combat in the village of Bint Jbeil.
The Shia militia said it killed four Israeli soldiers near the village of Houla, but Israel said a number of its troops were slightly wounded.
The clashes follow exchanges on Sunday, when Hezbollah rocket-fire killed 12 Israeli reservist soldiers in the town of Kfar Giladi and three people in the port of Haifa.
Israel said it had destroyed Hezbollah rocket launchers around Qana and Tyre that were used to attack Haifa.
The BBC's John Simpson in Tyre says the city, which now has only about 3,000 people left, many of them poor and elderly, has been cut off by Israeli bombing.
He says a crater blocks the farm track used to transport food and medicine to the city, and an Israeli spy drone flies overhead.
As fighting continues, UN Security Council members are expected to renew talks on the resolution aimed at stopping the conflict.
They are expected to discuss possible changes to a draft document to take account of Lebanese objections: Beirut is seeking a specific reference to a timetable for Israeli withdrawal from Lebanon.
Correspondents say no vote is likely until Tuesday at the earliest.
The text calls for an immediate cessation of hostilities and lays the groundwork for a second that would install an international peacekeeping force in southern Lebanon.
Senior Israeli officials have said they are broadly happy with the text.
Meanwhile, Arab foreign ministers and the head of the 22-nation Arab League, Amr Moussa, are holding an emergency session in Beirut to discuss the crisis.
They are widely expected to endorse Lebanon's position.