Al-Qa'ida force of 400 men besieged by Pakistani onslaught

The news from the front of the war on terrorism was all jitters and rumour yesterday, as Pakistani troops surrounding a suspected al-Qa'ida hideout in the north-western tribal areas faced a second day of ferocious resistance. Ayman al-Zawahri, Osama bin Laden's number two, was said to be the man the Pakistanis were closing in on.

The news from the front of the war on terrorism was all jitters and rumour yesterday, as Pakistani troops surrounding a suspected al-Qa'ida hideout in the north-western tribal areas faced a second day of ferocious resistance. Ayman al-Zawahri, Osama bin Laden's number two, was said to be the man the Pakistanis were closing in on.

Then it was reported that Zawahri and a handful of gunmen had escaped in an armoured vehicle at the start of the battle on Thursday. Then the story changed again, as unnamed military sources suggested the Egyptian radical with a $25m (£14m) bounty on his head had been wounded and was now being flushed out in house-to-house searches in the village of Shin Warsak, in southern Waziristan.

At one point yesterday, the Pakistani government even had to deny a rumour that Bin Laden himself had been captured. One official, speaking anonymously, told reporters that Bin Laden emphatically was not in the area, although he did not say how he could be so sure.

What was known, from reports on the ground and briefings in the Pakistani capital, Islamabad, was that a force of several thousand Pakistanis continued to pummel away at the suspected al-Qa'ida enclave with artillery and helicopter gunship attacks.

A spokesman for the Pakistani military, Major-General Shaukat Sultan, said the al-Qa'ida force numbered between 300 and 400. "This is an assessment from the fire we are receiving," he said. He acknowledged the al-Qa'ida forces were making attempts to break the siege and escape but he would not be drawn on speculation as to who might be trying to escape, or who might have already succeeded.

Unofficial sources claim 16 Pakistani soldiers and 24 militants were killed on Thursday, and another 15 Pakistanis were killed yesterday. One senior Pakistani security official, Brigadier Mehmood Shah, denied that there had been any Pakistani casualties.

The search for al-Qa'ida suspects in the rugged border region between Pakistan and Afghanistan has been fraught with ambiguities and fine political calculations from the moment that Bin Laden, Zawahri and an unknown number of other senior al-Qa'ida figures made their escape from the Tora Bora cave complex in southern Afghanistan in December 2001. The Pakistanis, backed to an unknown degree with help from the US, are engaged in a spring offensive to crack down on the fundamentalist strongholds of the tribal areas. However, given the longstanding links between the Pakistani intelligence services and the Taliban, which sheltered al-Qa'ida in Afghanistan until they were overthrown in the 2001 war, the delineation of friend and foe is far from clear.

And while the United States is anxious to reap the political benefit of capturing Bin Laden and Zawahri it is no longer entirely clear how valuable they still are in the broader war on al-Qa'ida and its radical anti-western affiliates.

Terrorism and security experts have repeatedly stressed that al-Qa'ida is not a top-down organisation - some even object to the use of the word "organisation" in any sense - and that any scope for planning and recruitment that Bin Laden might have had before the 11 September attacks has been severely compromised by his isolation. It is believed that he communicates only by hand-written note, regularly changes location and has contact only with a restricted circle of highly trusted confidants.

Events like the Madrid train bombings, meanwhile, suggest that the fight to suppress al-Qa'ida has spread to many different and unpredictable fronts, whose battle lines are almost certainly far away from the mountains of central Asia.

¿ All charges have been dropped against the US Army Muslim chaplain accused of mishandling classified documents at the Navy base in Guantanamo Bay, the Army said last night. Captain James Yee will be allowed to return to his previous duty station at Fort Lewis, near Tacoma, Washington.