JALALABAD, Afghanistan  -- Afghan commanders claimed Monday to have al Qaeda fighters cut off in eastern Afghanistan near where U.S. planes dropped the Pentagon's heaviest conventional bomb the day before
Eastern Alliance commander Hazrat Ali said Monday his forces had pushed Osama bin Laden's al Qaeda force into a 4-square-kilometer (1.5-square-mile) area of the White Mountains near Tora Bora.

Ali told CNN his troops had captured two enemy command centers and four tunnel complexes. The report could not be confirmed independently, but Ali said he is convinced bin Laden is in the area.

"We had information from the local population as well as our intelligence sources that he remains there," Ali said. "He was seen [Sunday], and people who were with him [Monday] were overhead speaking to him over their wireless."

He said the last reported sighting of bin Laden was four days ago and that bin Laden's deputy, Ayman al-Zawahiri, also was in the area.

The Eastern Alliance is a Pashtun-led group of anti-Taliban fighters in eastern Afghanistan.

The fighting occurred as U.S. bombers launched renewed strikes on the rugged White Mountains, near the Pakistani border.

Several dozen heavily armed U.S. troops were seen headed for the area to join Afghan fighters against an estimated 1,000 al Qaeda troops. Pentagon officials said U.S. intelligence also indicated bin Laden may be among them.

"The best indications of where he might be tend to point almost entirely, mostly to that area," Deputy Defense Secretary Paul Wolfowitz said Monday.

While intelligence on bin Laden's whereabouts is "very fragmentary and not very reliable," he said, "we don't have any credible evidence of him being in other parts of Afghanistan or outside Afghanistan."

In addition to attacks by heavy bombers and fighters, U.S. forces dropped a 15,000-pound "daisy cutter" bomb on a cave in the area Sunday.

"It was believed that that's where some substantial al Qaeda forces would be, and possibly including senior leadership," said Rear Adm. John Stufflebeem, a Pentagon spokesman.

Stufflebeem said the cave "should no longer be usable for anybody to get in or out of," but no one had been able to get close enough to see whether anyone had been killed.

Dropped by parachute from a cargo plane, the "daisy cutter" spreads a flammable slurry over a wide area before igniting it, killing nearly everyone within 600 feet of the blast. It is the largest conventional weapon in the U.S. arsenal.

The weapon has been used only twice before in Afghanistan, during the Northern Alliance's battle for Mazar-e Sharif.