Bin Laden deputy cornered

Several soldiers were killed today as the Pakistani army launched a final offensive against al Qaeda militants thought to be sheltering Osama Bin Laden's deputy.

As a deadline for the surrender of Ayman al Zawahri expired, thousands of troops poured forward, backed by helicopter gunships. "The operation is on," said military spokesman Major-General Shaukat Sultan.

At least 15 Pakistani soldiers have now died since the assault began last night and unconfirmed reports suggest al Zawahri was wounded during the heavy exchanges of fire near the town of Wana, in the mountainous South Waziristan tribal area of Pakistan.

Egyptian al Zawahri, 51, who is thought to have organised the September 11 attacks, is understood to be cornered in one of several mud-brick compounds being attacked from the air by helicopters and pounded with artillery.

A senior military official said: "A pitched battle is going on. The way these people are resisting, we think there is someone important over there. We think al Zawahri may be holed up there."

Pakistan's President Pervez Musharraf said the commander on the ground reported "fierce resistance" from fighters entrenched in fortress-like buildings. "He's sure there's a highvalue target there. They are not coming out, in spite of the fact that we pounded them with artillery."

A Wana resident said there were two loud explosions as helicopters hovered over the area after the deadline passed. Western officials are trying to determine whether Bin Laden is near al Zawahri - a surgeon who is believed to be Bin Laden's mentor as well as his deputy.

The US has placed a $25 million bounty on al Zawahri's head and is reported to have sent the commando unit involved in Saddam Hussein's capture to Waziristan. Along with Pakistani special forces, they are said to have planned a spring offensive to find Bin Laden and his deputy, long suspected to be in the area.

It was reported recently that Pakistani troops narrowly missed catching al Zawahri on the Afghan border. Most security officials agree he is unlikely to be taken alive.

The US administration and security experts were quick to play down the impact his capture or death would have on the war on terror. National security adviser Condoleezza Rice said: "Everybody has to be careful not to assume that getting one al Qaeda leader is going to break up the organisation. We have always said even with Bin Laden, who we would all like to see brought to justice, that will not be the end of al Qaeda. We have to dismantle the entire leadership, not just one person."

Former US National Security Council director Dan Benjamin said killing or capturing al Zawahri, or Bin Laden, would be more symbolic than practical.

He said: "If we got either, it would show the US ultimately does track down and get its enemies. As a practical matter in terms of the war on terror, I think the effect would probably be somewhat limited."

Mr Benjamin claimed al Qaeda has sprouted too many offshoots to be defeated by the capture of its leaders. "In many ways the war on terror has moved away from what was the core of al Qaeda. It is still very much there, but in a sense we are witnessing a new generation of jihadists coming to the fore."

Security analyst Ken Robinson said al Zawahri and Bin Laden were " connected at the hip", raising the possibility the al Qaeda leader could also be cornered. "It would be likely they would be near each other because of their close relationship," he said.

The surrounding of al Zawahri follows several anti-terror sweeps by Pakistani troops in the tribal regions in recent months.

The army has moved 70,000 troops into the region, which borders Afghanistan, with General Musharraf promising to rid the tribal areas of foreign terrorists. At least 41 people - 15 soldiers and 26 suspected militants - died on Tuesday in fighting in the area.