Associated Press WriterTORA BORA, Afghanistan (AP) -- With the hunt for Osama bin Laden now the main focus of the Afghan conflict, U.S. Marines moved closer to Kandahar on Monday to search for al-Qaida fighters. In the east, tribal fighters launched a three-pronged assault on pro-bin Laden warriors defending a mountain hide-out.
U.S. and Afghan officials regard both areas as likely bin Laden hiding places.
Marines also secured the abandoned grounds of the U.S. Embassy in the heart of Kabul -- the first time American troops have been seen in the capital since the Taliban fled last month.
In the south, a column of Marines with heavy weaponry and helicopters left their Camp Rhino in the desert southwest of Kandahar. They moved north to what a spokesman said are "key pieces of terrain" near the city, now under tribal control.
Kandahar, Afghanistan's second-largest city, had been the Taliban's last stronghold before a chaotic surrender Friday, when hundreds of pro-bin Laden fighters fled. The Marines have been trying to choke off their escape routes.
The Marines were blocking "roads and avenues of exit to capture al-Qaida and enemy forces," said spokesman Capt. Stewart Upton. "If the Taliban hold their weapons, they will die." He said the Marines would not enter Kandahar.
Another spokesman, Capt. David Romley, said Marines were being wary of unmarked minefields in the sandy and rocky landscape. "The closer you get to Kandahar the more dangerous it gets," he said.
Just after dawn in the east, U.S. airstrikes hit Tora Bora, a vast network of caverns and tunnels carved deep into the White Mountains.
After the bombardment, fighters from bin Laden's al-Qaida organization surfaced from their caves and fired mortars at tribal forces trying to move their aging Soviet-built T-55 tanks forward.
Hours later, small squads of tribal fighters launched an attack and advanced along mountain trails under the cover of tank fire.
Hafta Gul, a senior officer in the Eastern Shura's militia, said tribal forces were "attacking from three sides," while U.S. bombing paused to avoid hitting the fighters.
For days, more than 1,000 al-Qaida fighters have been defending two valleys and adjacent ridges with 82mm mortars and heavy machine guns.
Gul said Monday's objective was to capture the Milawa valley and a ridge overlooking the Tora Bora valley -- areas riddled with caves where the mainly Arab al-Qaida fighters shelter from bombs dropped by high-flying B-52s and other U.S. warplanes.
Meanwhile, Pakistani forces were deployed along the border near Tora Bora on Monday to stop al-Qaida forces from entering the country. Helicopters deployed personnel on mountain ridges to monitor the movement of the Islamic militants, witnesses said.
In Kabul, a Marine contingent swept the grounds of the U.S. Embassy while a State Department team went to work inside, in the first steps toward eventually re-establishing an American diplomatic presence in Afghanistan.
The United States closed the embassy in 1989, citing security concerns after the occupying Soviets left Afghanistan and feuding Afghan factions took over the capital.
Citing intelligence reports, U.S. officials, including Vice President Dick Cheney, and some Afghan commanders think bin Laden may be hiding somewhere near Tora Bora.
However, other Afghan officials say he has probably fled to mountains near Kandahar. Another fugitive, Taliban supreme leader Mullah Mohammed Omar is also thought to be on the run in the south.
On Sunday, Cheney said a videotape of bin Laden obtained by U.S. officials in Afghanistan makes clear that the al-Qaida leader was behind the terrorist attacks in the United States.
The Washington Post, quoting unidentified senior government officials, said the tape shows bin Laden praising Allah for the attacks, which he said were more successful than anticipated.
Marines are building a temporary prisoner of war camp outside of Camp Rhino.
Spokesman Capt. David Romley said fighters captured by Marines would be fed, given medical care and allowed visits by the international Red Cross for a short time until their status was determined.
John Walker, an American who fought with the Taliban, was recuperating at Camp Rhino as a "military detainee," said another spokesman, Capt. Stewart Upton.
Walker, 20, of Fairfax, Calif., was in good condition and was recovering from dehydration and a gunshot wound in the leg, Upton said.
Air Force Gen. Richard Myers, chairman of the U.S. Joint Chiefs of Staff, said Walker had been providing useful information and no final decision had been made on what to do with him.
EDITOR'S NOTE: Associated Press correspondents Kathy Gannon in Kabul, Afghanistan and Christopher Torchia in Quetta, Pakistan contributed to this report.