ISRAEL launched its deepest ground attack into Lebanon late last night when commandos raided a hospital and clashed with Hezbollah fighters in Baalbek, about 80 miles north of the border.

The commandos were reportedly searching for a senior Hezbollah figure, possibly Sheikh Muhammad Yazbek, a High Council member. Militants surrounded the hospital and fierce fighting broke out.

Witnesses said that the battle was still raging several hours after it started and casualities were reported. Israeli jets and helicopters attacked the area and dropped flares.

Hussein Rahal, the chief Hezbollah spokesman, said that Israeli troops were trapped inside the hospital. The military refused to comment, but sources said that four Israeli soldiers had been killed.

Mr Rahal dismissed reports that the commandos snatched patients from the hospital and removed them by helicopter.

The raid was the first time that Israeli forces had ventured so far into Lebanon since 1994.

Thousands of Israeli troops were fighting Hezbollah across a wide strip of southern Lebanon yesterday as the Israeli Government declared that it intends to seize territory up to the Litani river.

Tanks and armoured bulldozers were massing along roads on the Israeli side of the border after the security Cabinet approved an expanded ground operation.

Early today, as the 48-hour pause in aerial attacks expired, Israeli jets could be heard thundering over the border into southern Lebanon.

In Taibeh, a town in the shadow of the Crusaders’ ancient Beaufort Castle, Israeli generals claimed last night that troops had seized a crucial stretch of the Litani river, about 18 miles north of the border .

Yesterday’s fighting, which took in Taibe, Adaisseh and Aita al-Shaab — where Hezbollah said it had destroyed an Israeli tank killing three soldiers — is widely regarded as part of the build-up to a larger-scale Israeli ground advance.

The army said that it had distributed leaflets northeast of the Litani in villages where Hezbollah was active, warning residents to leave.

With international criticism mounting, the Israeli Government senses that time is running out to achieve its objectives, and obtain a ceasefire on its terms.

“The next few days will be critical,” Amir Peretz, the Defence Minister, said. He added that the troops aimed to secure the ground so that an international stabilisation force could take control. “It will determine the chances of whether in future a terror organisation might dare to hit the Israeli home front. The intention is to create new conditions.”

Tzipi Livni, the Foreign Minister, acknowledged that the attack on the Lebanese village of Qana had marked a turning point, cutting Israel’s room for diplomatic manoeuvre.

Ehud Olmert, the Prime Minister, said that he would not agree to an immediate ceasefire. “Every additional day is a day that weakens this cruel enemy. Every additional day is one where the Israel Defence Forces’ soldiers minimise Hezbollah’s ability to fire missiles and threaten Israel,” he said.

“We will agree to a ceasefire only when we know the conditions on the ground are different from those that brought the outbreak of war.”

Mr Olmert’s Cabinet has ordered the army to push north to seize land up to the Litani, as deep as 18 miles (29km) from the border. Military chiefs have been given more than a week to complete the task, but said that they believed they could achieve their objectives within seven days or less.

Danny Yatom, a reserve general who sits on the Cabinet committee, said: “I think they just need a few days, or the maximum of a week to get to the Litani.”

The MP said that 90 per cent of Hezbollah’s Katyusha missiles were short-range rockets and those fired into Israeli towns were shot from areas south of the Litani. “Once we control that area, by and large they will not be able to fire those rockets,” he said. “It will not be possible to stop the rockets totally, but their chances of firing from north of the Litani will be much more limited.”

But Israel is adamant that it will leave southern Lebanon only once a ceasefire is declared after the arrival of the international force, fearing that otherwise, Hezbollah would simply fill the vacuum.

Brigadier General Shuki Shachar said that his Northern Command forces aimed to “control” areas and to hold the terrain. Some units even moved quickly through certain regions, he said, “bypassing” built-up areas.

Some of his forces had “raced to the front” to cut off Hezbollah’s resupply and retreat. Others stayed in areas to “clean” them. In others they went “systematically from the south to north to capture as many Hezbollah as possible”.

“Along the border we clean a wide zone, destroying all the Hezbollah positions that they used before July 2006, and we continue to clean the whole area of any future bases.”

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