Osama bin Laden’s cement-lined swimming pool fed by a mountain stream still lies, half destroyed, at the entrance to his cave complex at Tora Bora.

Close to the caves, which have been dynamited shut, is a rusting 1980s Soviet tank; bullets and scraps of camouflage clothing litter the ground. An air of brooding gloom hangs about the cloud-wreathed mountains.

But six years after American Special Forces failed to capture the Qaeda leader in his mountain stronghold, the place where the September 11, 2001, attacks were allegedly hatched, American troops are again scouring the mountains of Tora Bora.

A week ago, American forces launched a major operation to counter a rejuvenated Al Qaeda, which has been steadily regrouping in the tribal areas of Pakistan, and has in the past three months moved back into the Tora Bora area of Afghanistan.

American military officials say much of what is happening around Tora Bora remains “classified.” Discreetly, Western officials in Kabul describe it as “very successful,” trapping insurgents in a series of adjacent valleys. Local people report that the fighters include Arabs, Chinese Muslims, Chechens, and a large contingent of Uzbeks led by Tahir Yuldashev. The Uzbeks are a surviving remnant of the Islamic Movement of Uzbekistan, a Qaeda affiliate that fought with the Taliban against the Americans in 2001.

Its surviving members fled into Pakistan’s lawless tribal belt where, earlier this year, their hosts turned against them following a dispute. Afghan leaders say that the Uzbeks were recently given the choice to fight the Americans in Afghanistan or face annihilation by the local tribes. At least one sizable group of Al Qaeda and Taliban fighters is continuing to resist despite heavy bombing raids and attacks from American Special Forces. American military spokesmen declined to corroborate the claim, saying the operation was ongoing.

“The bombing has been heavier than it was in 2001,” said Haji Tahir, a prominent tribal leader who asked for his name to be changed because of the certainty of reprisals. Other fighters have been dispersed into the surrounding peaks and gorges.

“Five hundred infiltrated the area,” said General Qadim Shah, the commander of the Afghan army’s 1st Brigade in Nangahar. “We have captured 57 fighters from the Taliban and Al Qaeda. They include Chechens, Arabs, and Uzbeks.”

Tribal leaders said these include several men known locally as longstanding Afghan figures in the Qaeda leadership.

General Dan McNeill, the NATO commander, moved a battalion from 82nd Airborne, which makes up his operational reserve in Afghanistan, from Helmand to support the operation. Pakistani troops are also reported to have taken up blocking positions along the border. The Daily Telegraph was the first Western newspaper to reach the area of the fighting, thanks to help from local tribesmen who smuggled Americans in along the only access road. Three American Special Forces soldiers and their translator were killed on the approaches to the caves last week and Western officials say that two helicopters have also been damaged in the fighting.

It took several hours on foot, accompanied by a small group of armed tribesmen and an Afghan intelligence officer, to reach the cave complex that Mr. bin Laden built prior to 2001. Taliban fighters had last been reported in the area the day before, when they severely beat a number of local villagers. The intelligence officer contacted American forces by phone to forestall the danger of an air attack.

Newly built Taliban stone firing positions were visible close to the track. So too were American propaganda leaflets carrying sinister images of silhouetted Al Qaeda and Taliban fighters with white glowing eyes. Dropped as the operation began, they warn local people not to aid the insurgents.

Four hundred families are reported displaced from the remote area and at least seven local people killed by bombing.

“We came back yesterday night,” said Noor Mohammad Khan, who farms near Tora Bora in an area called Milawa.

“We are very scared. Every night they are bombing the next valley. Last night, they dropped troops from helicopters on the top of this hill and they walked through this area.”

In 2001 the American was criticized for relying on local militias, who reputedly took bribes to allow the majority of Al Qaeda’s key leadership to escape. This time, American forces were dropped into the area by helicopter, blocking escape routes to the border.

The growing presence of Al Qaeda and Taliban fighters in the area was first noted around two and a half months ago. Taliban “night letters” in local villages announced a new “Tora Bora Front” under the leadership of Maulawi Anwar ul-Haq Mujahed, the son of the prominent mujahedeen commander Younis Khalis, who fought the Soviet occupation. An important Qaeda figure, Dr. Amin ul-Haq, who has been listed by the American government as Mr. bin Laden’s security coordinator, was also with the force. Local leaders say Dr. Amin was injured in a bombing raid and smuggled back across the border.

“I don’t think that the biggest Al Qaeda people are on this side of the border, but they are close by, just over the border,” said one local tribal leader.

Western intelligence has placed Mr. bin Laden close to the border, probably in the tribal region of Khurram, which lies across from Tora Bora, during recent months.