Associated Press WriterTORA BORA, Afghanistan (AP) -- Backed by intensifying U.S. airstrikes, Afghan tribal fighters launched a new assault Thursday against trapped al-Qaida forces. Commanders said key terrorist leaders had likely fled Osama bin Laden's besieged mountain base for neighboring Pakistan.
The whereabouts of bin Laden remained unknown.
Front-line commanders of the tribal eastern alliance said they now intended to wipe out the Arab and foreign Muslim fighters from al-Qaida after two deadlines to surrender fell through over the past two days -- the latest at noon Thursday.
AC-130 gunships, armored aircraft with Gatling guns, strafed al-Qaida positions as B-52s circled over the canyon where the foreign fighters have been trapped since fleeing their nearby Tora Bora cave complex in the eastern White Mountains three days ago.
At least one 15,000-pound "daisy cutter" -- and perhaps as many as three -- was dropped before dawn. An Associated Press reporter saw a huge, bright magenta fireball that hung in the air and lighted the sky around 3 a.m.
Meanwhile, Afghanistan's interim leader, Hamid Karzai, slipped into the curfew-shrouded capital overnight in his first visit to Kabul since being named to head a post-Taliban government. With his temporary administration due to take office in nine days, Karzai met top officials in Kabul.
In the southern city of Kandahar, a group of al-Qaida fighters hospitalized with wounds from battle threatened to blow themselves up if anyone other than medical staff entered their rooms. The men, who were strapped with explosives, apparently feared retribution by Afghan tribal forces who took over the city from the Taliban.
Snow fell Thursday afternoon over the Tora Bora area, making it more difficult for the al-Qaida holdouts to escape their heavily forested canyon.
After an initial easy advance, tribal forces met mortar and machine gunfire from the al-Qaida holdouts, said Hazrat Ali, a senior alliance member. He estimated the number of foreign fighters at around 700.
"The al-Qaida forces are about to be finished," said one front-line commander, who identified himself only as Hamid. "They don't have any more food or ammunition."
Hamid said Thursday's assault was ordered after it became clear that senior al-Qaida chiefs had left the Tora Bora area and abandoned their rank-and-file troops.
Fleeing leaders might try to cross the Pakistan border, just a few miles south across the snowcapped White Mountain range, he said. Pakistan has reinforced the border to prevent al-Qaida incursions.
It was unclear why the Afghans thought major al-Qaida figures had taken part in the defense of Tora Bora, which has seen some of fiercest fighting of the war in Afghanistan.
Several figures of the eastern alliance had offered vague, secondhand accounts of seeing bin Laden, but U.S. Deputy Defense Secretary Paul Wolfowitz questioned their accuracy.
The $25 million U.S. bounty on bin Laden was a powerful incentive for the Afghan militias to lay siege to Tora Bora.
"We do not know who is escaping and who is not" or whether any senior leaders were among the al-Qaida forces to begin with, Gen. Peter Pace, vice chairman of the U.S. Joint Chiefs of Staff, said in Washington when asked by a reporter Wednesday about al-Qaida fighters in the Tora Bora cave complex.
Bombing was relentless Wednesday night and Thursday morning as U.S. special forces deployed by helicopters helped target airstrikes.
After one jet dropped 1,000-pound bombs on an al-Qaida post, an Afghan soldier on the ground could be heard cheering over the alliance's radio network.
"Thank you. Thank you very much," he said in English after the target was reduced to a smoking heap of rubble.
Pentagon officials said the bombs included satellite-guided weapons that home in on their targets and the "daisy cutter," the biggest conventional bomb in the U.S. arsenal, which obliterates everything within a few hundred yards when it explodes.
Casualty figures from the latest bombardment were not known.
U.S. officials said it was not clear whether some enemy personnel were still sheltering in the hundreds of caves and tunnels that riddle the area.
Thursday's fighting came after two surrender deals between the alliance and al-Qaida troops fell through.
After an initial deal failed on Wednesday, tribal commanders set a new deadline of midday Thursday for trapped al-Qaida fighters to give up, but added a demand that their leaders be handed over as well.
The alliance said that some of those leaders are on a list of 22 "most wanted terrorists" made public by Washington after the Sept. 11 terror attacks in the United States.
Meanwhile, 13 injured Arab fighters in a Kandahar hospital lay in their beds with grenades and explosives strapped to their waists, said Ghulam Mohammed Afghan, head nurse at Mirwais Hospital. They demanded only a few nurses be allowed into their rooms, apparently fearing the numerous Afghan fighters who are present at the hospital.
When the Taliban surrendered the city a week ago, tribal fighters allowed Afghan members of the former ruling militia to go home. But Arabs and other non-Afghan fighters -- particularly hated by the anti-Taliban forces -- face imprisonment or worse.
The hospital is guarded by forces loyal to Mullah Naqibullah, who helped broker the Taliban's surrender of Kandahar but has been accused of being too close to the Islamic militia.
The nearest cluster of U.S. troops on Thursday were special forces about six miles away.
In the eastern city of Jalalabad, 200 Pakistani prisoners who fought alongside the Taliban were released Wednesday and were making their way home.
The release was made to mark of Islam's upcoming Eid al-Fitr feast that follows the Ramadan fasting month, said Azrat Ali, a senior alliance commander. More releases could be made soon, he said.