Even as the Israeli Cabinet unanimously approved a cessation of hostilities for 8am local time (6am BST) today, Fouad Siniora, the Lebanese Prime Minister, was struggling to keep the peace plan alive.

A senior Lebanese government official told The Times that Hezbollah was refusing to give up any of its weapons or to move out of an agreed “arms-free zone” south of the Litani river. As he spoke, 30,000 Israeli troops waged a fierce ground offensive against Hezbollah fighters in southern Lebanon and Israeli jets bombed more than 50 towns and villages as well as Beirut.

A scheduled Cabinet meeting in Beirut to finalise plans to deploy 15,000 Lebanese troops to police the UN-mandated buffer zone was postponed after the two Hezbollah ministers in the coalition Government threatened to boycott it.

“Hezbollah changed its position, going back on what was agreed unanimously during Saturday’s Cabinet meeting to support the ceasefire proposals and immediately deploy the Lebanese Army,” the senior Lebanese official said.

At the UN, officials said that the organisation was taking a “wait-and-see” approach until fighting subsides. A French military planning team is due to hold talks at the UN headquarters in New York today on the dispatch of a 15,000-strong UN force to work with the Lebanese Army to take over Israeli positions in the buffer zone, 20km (12 miles) wide.

Israel used the countdown to the ceasefire to try to kill Sheikh Hassan Nasrallah, the Hezbollah leader, by bombing what it believed was his underground hideout in Beirut.

In the fiercest bombardment that the capital has felt since this conflict began, 23 missiles landed in the southern suburbs within two minutes from Israeli jets and warships.

The main target was an apartment block in the Rweiss neighbourhood, where Israeli officials claimed Hezbollah leaders were using a basement as a command-and-control centre.

Rescue workers clawed at the wreckage of eight buildings and a mosque, which were destroyed in the attacks.

Hezbollah released a statement last night claiming that Sheikh Nasrallah and his key lieutenants were safe and had not been in the area.

After news of the postponement of the Cabinet meeting was announced in Beirut, there were five more strikes on the same area of the capital.

Israel also stepped up its air and artillery blitz against south Lebanon, with Israeli troops pressing to take control of as much territory as possible toward the Litani river before the scheduled truce.

Last night Israeli airstrikes on Brital in eastern Lebanon killed at least seven people and wounded thirty-five. Earlier, Israeli aircraft has attacked at least seven petrol stations in and around Tyre, killing up to fifteen people. In the village of Bourj Shemali, two miles east of Tyre, a mother and her three children, as well as a Sri Lankan maid, were killed when their house was destroyed in an air raid.

Despite the Israeli offensive, more than 250 Hezbollah rockets were fired into northern Israel, including seven long-range missiles, killing a man of 70 and wounding 53.

Yesterday’s tally — the highest to date — took the total since fighting began on July 12 to more than 4,000 rockets.

Even if today’s ceasefire is observed, it will leave Israeli forces and Hezbollah guerrillas intermingled on isolated patches of territory with no clear front line to separate them.

Hezbollah units repulsed Israel armoured thrusts, killing 24 Israeli soldiers on Saturday, the worst casualty toll in one day for Israeli troops since the conflict began. At least five soldiers died yesterday.

Ehud Olmert, the Israeli Prime Minister, faced heavy domestic criticism for his conduct of the war. In the Haaretz newspaper, Moshe Arens said that Mr Olmert, Amir Peretz, the Defence Minister, and Tzipi Livni, the Foreign Minister, “are not fit to govern Israel in these trying times”.

Times Recommends

• 'Great Schlep' may seal deal for Obama
• Hindu 'storm troopers' flex their muscles
• Ahtisaari: deserved reward for (failed) plan