Opposition fighters are moving through the cave and tunnel complex near Tora Bora in the search for Osama bin Laden and the senior leaders of the al-Qaeda terrorist network, the Pentagon said yesterday.
Supported by US air strikes, the tribal fighters have begun the perilous work of combing the caves one by one, amid the White Mountains some 70 km south-west of Jalalabad.
Senior US officials think the fortified complex is the most recent hideout for bin Laden and several thousand heavily armed al-Qaeda fighters. US special operations forces are now working alongside the opposition fighters to direct air strikes on cave entrances where they are confronting al-Qaeda fighters.
Gen Peter Pace, vice-chairman of the joint chiefs of staff, said in Washington yesterday that co-ordination with local fighters allowed far more effective use of bunker-busting bombs weighing up to 900 kg. "Until just recently, we haven't been attacking the caves from the air," he said at the Pentagon yesterday.
"Now as the opposition groups move their troops through that complex, we're able to provide them the air support that they can help direct," he said. "Because they're able to see the caves that are active, they can see the caves that are not, and we're able to provide much more direct support for them."
Reports from Afghanistan suggested that local opposition fighters in the Tora Bora area were gaining confidence as they claimed to have killed two dozen al-Qaeda fighters.
Ayman al-Zawahri, one of the founders of al-Qaeda alongside bin Laden, was reported to have been injured in one attack on Tora Bora this week.
The reports have not been confirmed, although the official spokesman for the British prime minister, Mr Tony Blair, said there were "persistent reports" that al-Zawahri had been killed.
As the winter snow begins to close down supply routes leading to the caves, US officials think they may be able to tighten the net around Tora Bora more effectively, at the same time as using infra-red detection to direct strikes against those hiding in the bitterly cold mountains.
US forces have been monitoring the Tora Bora area since the fall of Kabul, after local reports emerged that al-Qaeda had paid villagers $50 a family to leave the area.
The network of caves was one of the most effective bases for the anti-Soviet rebels in the 1980s.
To the south-west in Kandahar, the US bombing, a trickle of defections from senior ministers which gradually became a flood, and the offer of individual survival in return for surrender were the crucial factors which finally led Mullah Mohammed Omar, the Taliban's supreme leader, to throw in the towel yesterday.
His decision to give up control of Kandahar will end the agony of the air strikes which has sent an estimated 400,000 civilians fleeing in terror out of the city, either into the countryside or towards the Pakistani border. Thousands have been forced to sleep in the open with little or no shelter in sub-zero night-time temperatures. Several children have died.
The pressures on the Taliban leadership had grown intense in the past few days as Mr Hamid Karzai, a noted Pashtun chief of the Popolzai tribe and the newly nominated head of Afghanistan's next government, pushed south towards Kandahar.