“He has not yet been captured,” said Hazrat Ali, commander of Afghan anti-Taliban forces advancing cave by cave against Al-Qaida fighters burrowed into the Tora Bora, or black dust, canyons.

Hundreds of Al-Qaida fighters, mainly Arabs, had been killed in days of relentless U.S. Bombing from the skies and by Afghan fighters inching forward on the ground, he told Reuters early today.

Huge U.S. B-52 bombers raced through the skies on the first day of Id festival that celebrates the end of the holy fasting month of Ramadan, dropping huge bombs on suspected Al-Qaida positions through the night and into the morning.

U.S. Defense Secretary Donald Rumsfeld arrived at an airbase north of the capital Kabul where he was to address American troops.

He said the bombing around Tora Bora was intense, with more than 200 bombs dropped at the weekend alone.

Those strikes appeared to make surrender by besieged Al-Qaida forces impossible - even if they wanted to.

“We asked them to give themselves up, but they can’t because bombs keep falling,” Haji Atiqullah, spokesman for frontline Tora Bora commander Haji Zahir, told Reuters. It was possible U.S. forces wanted to thwart a surrender, preferring not to see Al-Qaida fighters taken prisoners, he said.

Atiqullah said his anti-Taliban mujahideen fighters captured three Arab Al-Qaida members in the night, two of them wounded.

Fuelling their determination to hunt down the Saudi-born millionaire blamed for masterminding the September 11 attacks on the USA that killed more than 3,000 persons would be reports that his voice had been heard in the area.

The Al-Qaida leader had been heard giving orders on a short-range radio in the past few days in the Tora Bora region, the last pocket of Al-Qaida resistance, a U.S. official said.

The whereabouts of Bin Laden remained a mystery, with U.S. officials saying he could still be with his cornered fighters.

His men, numbering up to 1,000, appeared determined and hints of surrender were being seen by some frontline commanders as little more than ploys to buy time by embattled fighters in the mountains about 40 km (25 miles) south of the eastern city of Jalalabad.

Seeking evidence against Bin Laden, Rumsfeld said the latest intelligence material had been found at the Tarnak Farms Al-Qaida base, about 6 km (four miles) east of a U.S. Marine desert base known as Camp Rhino.

It was on a list of 25 or 30 sites that have been systematically reviewed by American forces as they came available in Afghanistan.

Speaking at a base that could not be identified for security reasons, Mr Rumsfeld said the materials had been found in the past 24 hours. He did not say whether actual weapons had been found, stressing that intelligence and materials were being examined.