Some U.S. intelligence officials now believe that terrorist mastermind Osama bin Laden and Taliban leader Mullah Mohammed Omar have escaped from Afghanistan and are now being sheltered in remote tribal-controlled regions of Pakistan, U.S. News has learned.

Even as U.S. warplanes continue to pound the al Qaeda mountain fortress at Tora Bora, the two wanted men are believed to be sheltered in separate locations by Pakistani tribesmen in lawless regions of the Northwest Frontier province that borders Afghanistan, sources say.

Bin Laden may be heading towards Pakistani-controlled Kashmir, where he has supported terrorist groups in the past, some intelligence reports suggest. Most important would be the violent group Harakat ul-Mujahidin, which boasts thousands of armed supporters, including Arab veterans of the Afghan war. His presence in war-torn Kashmir could vastly complicate U.S. efforts to capture or kill bin Laden, in part because India could use his being there as a pretext to enter parts of the disputed territory-a move that would risk inciting another India-Pakistan war.

But Pakistani troops have a heavy presence in Kashmir, and other intelligence experts believe that he may be safer staying in the tribal-controlled regions of Pakistan until he can secure passage to a third country. Pakistan has dispatched reinforcements to the border in order to intercept fleeing al Qaeda operatives, but much of the area is divided into autonomous tribal lands with little Pakistani government presence. Many of the tribesmen there share the same Pashtun ethnic heritage as the fugitive Taliban leader. "There is a lot of sympathy for the Taliban there and it's Wild West country," says one government analyst. "It would be a lot harder for the Pakistan government to root him out."

Other U.S. officials are more cautious. "Bin Laden is believed to be in Afghanistan, but we cannot rule out the possibility that he may have left the country," says one U.S. official. Just yesterday, Secretary of Defense Donald Rumsfeld repeated his belief that bin Laden and Omar remained in Afghanistan. Still, an intelligence source insists the reports of their flight "is not just speculation." An interview with an al Qaeda operative conducted this week by a U.S. News special correspondent in Tora Bora may provide further confirmation of bin Laden's location. Abu Jaffar, a mid-level al Qaeda member, described how bin Laden traveled out of Tora Bora twice during the holy month of Ramadan. The second time, Jaffar said, bin Laden left about 10 days ago towards Pakistan, "where he was helped across the border by Pashtun tribesmen."