U.S. B-52 bombers carried out heavy strikes against Taleban front-line positions north of Kabul Friday. The strikes took place as Taleban authorities searched for a key ally of Afghanistan's exiled king, who entered Taleban territory more than a week ago to meet with tribal leaders.

Northern Alliance troops who witnessed the intense bombardment say B-52 bombers struck Taleban front line positions and rear areas. A key target was the Tutakhan hills north of Kabul which overlook the strategic Bagram air base. Northern Alliance forces hold the base but cannot use it because of Taleban positions that overlook it.

Northern Alliance fighters told western reporters after the latest raids that the strikes were the heaviest since the United States began using the massive four-engine B-52s to hit Taleban front line positions.

Some Alliance fighters say there were too many bombs dropped in the latest raid to count. Huge explosions kicked up clouds of dust and smoke. Unconfirmed reports say a number of Taleban tanks were destroyed in the attacks, which are meant to soften up entrenched positions and clear the way for a long awaited Northern Alliance attack.

U.S. Defense Secretary Donald Rumsfeld said Thursday that small numbers of American special forces were on the ground helping identify targets and officials have indicated that more U.S. troops are on the way.

Meanwhile, Taleban forces on Friday were searching for Hamid Karzai, a key aide to Afghanistan's ex-King Zahir Shah, and former deputy foreign minister of Afghanistan. The Pashtun tribal leader slipped into Afghanistan about 10 days ago to meet with other Pashtun tribal leaders who might be willing to oppose the Taleban.

Taleban authorities say they attacked Hamid Karzai's camp on Thursday, capturing about 25 of his followers, but he and several others managed to escape. Talat Masood is a retired Pakistani General who closely follows Afghan exile politics in Pakistan. He says the fact that Hamid Karzai has so far managed to elude Taleban capture shows there is the potential for opposition to develop to the Taleban in traditional Pashtun tribal areas.

"This shows there are people in Afghanistan who are protecting him, which goes to show there is dissent, and there are groups which are likely to come forward, provided they see that there is any alternate government which is shaping up," he said.

Taleban authorities said on Friday that several of Hamid Karzais colleagues who were captured on Thursday would be taken to Kandahar and hanged, but so far there has been independent confirmation of the Taleban carrying out their threat.

Last month the Taleban captured and executed Abdul Haq, a former Pashtun Mujahiden leader who had returned from exile in Dubai to try and raise a rebellion against the Taleban in Pashtun tribal areas. Talat Masood, has said Hamid Karzai has closer ties to people in the region than did the legendary former Mujahiden commander.

"Hamid Karzai is more important because he has been keeping in touch with the people and going in and out of Afghanistan, from Quetta to Kandahar and other places. He has contacts and I think he is more genuine as well in the sense he has more roots and he has been very active as an opposition leader. He was also one of the deputy ministers in the Rabbani government," he said.

Hamid Karzai recently played a key role in organizing a large gathering of Afghan tribal leaders, and former Mujahiden commanders in the Pakistani city of Peshawar. The meeting was aimed at building support for a broad-based post-Taleban government in Afghanistan under the banner of former King Zahir Shah.