Israel last night bowed to international pressure and agreed to a 48-hour suspension of aerial activity over southern Lebanon after more than 50 civilians - half of them children - were killed in the deadliest Israeli airstrike so far.

The suspension was announced by US State Department spokesman Adam Ereli, who said Israel reserved the right to attack targets if it learns that attacks are being prepared against them.

Mr Ereli also said Israel would co-ordinate with the United Nations to allow a 24-hour period of safe passage for people living in south Lebanon who wanted to leave the region.

The news came after an air strike by Israel on the Lebanese village of Qana hit a three-storey house where families were sheltering in the basement.

Survivors scrabbled through debris to reach loved ones, while some aid workers were so overcome that they sat among the rubble and wept.

The death toll, which rose steadily throughout the day, stood at nearly 60 last night. Most of those killed appear to have been children and elderly people.

Much of the world quickly lined up to condemn the strike, and renewed their calls for an immediate ceasefire.

UN Secretary General Kofi Anan urged an immediate halt to hostilities at an emergency meeting of the Security Council in New York.

The Pope also insisted the violence had to stop straight away.

Yesterday, Prime Minister Tony Blair was trying to broker an international agreement to end the bloodshed in the Middle East.

Mr Blair has faced anger at home and abroad for his reluctance to call for an immediate end to Israeli hostilities in Lebanon.

But last night he said he believed there was now a basis for a resolution that would lead to a ceasefire.

Negotiations were also taking place to hammer out a UN resolution that would mandate an international "stabilisation force" for Lebanon, and aim to set the parameters for a lasting peace.

An emergency session of the UN Security Council was under way in New York last night, where the resolution was top of the agenda.

A joint statement issued by Britain and Germany said yesterday's destruction of Qana underlined "the need for a ceasefire as soon as possible".

But Mr Blair still would not commit himself to calling for an immediate end to the fighting.

As well as criticism abroad, the Prime Minister is also facing a damaging Cabinet split after Jack Straw broke ranks to warn that Israel's actions risked destabilising Lebanon.

Mr Straw, the Leader of the Commons and a former Foreign Secretary, said that while he grieved for innocent Israelis killed, he also mourned the "ten times as many innocent Lebanese men, women and children killed by Israeli fire".

He added: "These are not surgical strikes, but have instead caused death and misery amongst innocent civilians."

Yesterday's attack on Qana prompted Mr Blair to interrupt his schedule during an official visit to San Francisco to hold talks with a series of world leaders, including US President George Bush.

He also held telephone talks with the Prime Minister of Lebanon, Fouad Siniora, who insisted there was "no room" for negotiation until Israel halted its attacks.

At a Press conference Mr Blair said: "We have to speed this entire process up, get a (United Nations) resolution now, and on the passing of an agreement of that resolution, then the hostilities have got to stop, and stop on all sides."

But he repeated his call for diplomacy to address the underlying problems, and not just the immediate fighting.

"We have got to make sure that the discussions that we're having, and the negotiations that we're conducting, do lead to a genuine cessation of hostilities, in a way that allows us to put an end to them for good," he said.