VIOLENCE was stepped up by both sides in the Middle East conflict yesterday, as diplomats in New York tried to reach agreement on a United Nations Security Council resolution to stop the bloodshed.

Lebanese militant group Hezbollah fired a massive barrage of 80 rockets into towns in northern Israel, killing at least 15 people, including 12 reserve soldiers, in the costliest day for Israel since the crisis began on July 12.

An Israeli bombardment killed at least 14 people in southern Lebanon, with some villages facing constant bombing for as long as half an hour, while warplanes fired at least six missiles into the capital Beirut.

Both sides seemed to be taking advantage of what little time remains to them to inflict damage on one another before agreement - expected today or tomorrow - of the draft resolution thrashed out by the US and France, which calls for a "full cessation of hostilities" in the region.

Prime Minister Tony Blair yesterday spoke by phone with US President George Bush and Russian President Vladimir Putin, and was last night planning to talk to French President Jacques Chirac.

Downing Street said the PM was stressing the need to get the resolution agreed as quickly as possible. He believed events on the ground "made the need to bring about an end to the hostilities even clearer", said a spokeswoman.

Mr Blair has received phone briefings on the humanitarian situation in Lebanon from both Christian Aid and Oxfam over the past two days.

He was also briefed by Britain's UN ambassador Sir Emyr Jones Parry and Foreign Secretary Margaret Beckett about efforts to achieve agreement in the 15-nation Security Council.

However, as agreement came closer at the UN, doubts were raised over whether the warring parties would comply with a resolution calling for them to lay down their arms.

Lebanon's parliamentary speaker, Nabih Berri, who represents Hezbollah in negotiations, said Beirut would reject the plan because it did not deal with key demands for Israel to release prisoners, resolve a border dispute and remove its troops from Lebanese soil.

Meanwhile, Israeli justice minister Haim Ramon, who is close to Prime Minister Ehud Olmert, said the country's forces would remain in southern Lebanon until the deployment of a proposed stabilisation force.

"Even if it is passed, it is doubtful that Hezbollah will honour the resolution and halt its fire," he said.

"Therefore we have to continue fighting, continue hitting anyone we can hit in Hezbollah, and I assume that as long as that goes on, Israel's position, diplomatically and militarily, will improve."

There were also ominous signs that key players are contemplating a broadening of the scope of the current conflict.

Israel's ambassador to the UN, David Gillerman, warned that his country would regard a Hezbollah rocket attack on Tel Aviv as an act of war by the group's Iranian backers.

He told the BBC: "Hezbollah would not dare to launch rockets at Tel Aviv without specific orders from Iran. If there are rockets fired at Tel Aviv, this will actually be a direct act of war and an order by Iran carried out by Hezbollah and I think the implications are very clear."

And Syria's foreign minister Walid Moallem, on a visit to Beirut, warned: "If Israel attacks Syria by any means, on the ground, by air, our leadership has ordered the armed forces to reply immediately."

US Secretary of State Condoleezza Rice said the resolution being discussed at the Security Council was "the first step, not the only step". It would be followed by a second resolution to establish a stabilisation force.