BANGI, Afghanistan (AP) In a decisive move to strike at the last Taliban stronghold, hundreds of U.S. Marines landed by helicopter early today near the southern Afghan city of Kandahar, a senior U.S. official said. As many as 1,000 troops could be on the ground there within days.

The deployment of the first large U.S. ground expeditionary force comes a day after the Taliban"s last northern garrison, Kunduz, fell to troops of the northern alliance, and a bloody, chaotic jailhouse uprising by some of the foreign fighters captured in that siege.

Sending in the Marines marks a perilous new phase of a conflict that until now has been focused on U.S. airstrikes backing up the opposition northern alliance, plus limited ground missions by several hundred American special forces fanned out in small units across Afghanistan.

Kandahar, the Taliban"s home base and spiritual home, has come under fierce bombardment since the conflict began Oct. 7, and the Taliban have vowed to fight to the death rather than abandon the city. In the last three weeks, they have lost their grip on three-quarters of Afghanistan, plus the capital, Kabul.

Most of the top Taliban leadership is believed to be holed up in and around the city. Efforts by tribal leaders over the past 10 days to negotiate a handover of the city failed to yield results.

Abdul Jabbar, an anti-Taliban Afghan tribal official in Pakistan, said his colleagues in Kandahar confirmed that U.S. troops were on the ground there.

The Marines, numbering in the "low hundreds," were to be followed by several hundred more from Navy ships in the Arabian Sea, the U.S. official said in Washington, on condition of anonymity. The Marines landed by helicopter southwest of Kandahar, the official said.

The fall of Kunduz, which came two days before talks were to begin in Germany on forming a broad-based government, leaves the Islamic militia with only a small share of Afghanistan still under its control, mostly around Kandahar.

Thousands of Taliban troops as well as Arab, Chechen, Pakistani and other foreign fighters linked to Osama bin Laden had been holed up in Kunduz, which the alliance said fell almost without a fight.

Pro-Taliban fighters including foreigners fled yesterday toward the town of Chardara, to the west, with alliance troops in pursuit, alliance acting foreign minister, Abdullah, said by satellite telephone from the north of Afghanistan.

While some chose to make a run for it, thousands of others surrendered by the thousands as northern alliance troops moved in. Under a pact negotiated earlier between the alliance and the Taliban, Afghan Taliban fighters were guaranteed safe passage out of the city but the foreigners were to be arrested pending investigation into possible ties to bin Laden.

Outside the city of Mazar-e-Sharif, 100 miles to the west, hundreds of foreigners who had been captured earlier in the Kunduz area staged a violent uprising at their prison fortress, triggering a fierce daylong battle with northern alliance guards. U.S. aircraft helped quash the insurrection.

Hundreds of foreign Taliban prisoners were killed, U.S. and alliance officials said.

A U.S. special forces soldier inside the Qalai Janghi fortress was taped by a German television crew saying an American may have died.

But Pentagon officials in Washington later said all U.S. troops were accounted for and none had died. A U.S. government official, speaking on condition of anonymity, said later in Washington that a CIA operative was wounded in the uprising.

Dave Culler, a spokesman for the U.S. Central Command, which oversees the war in Afghanistan, suggested that the uprising was in effect a suicide mission. At least one foreign fighter had killed himself Saturday while surrendering, witnesses said giving himself up, then setting off a hand grenade when an alliance officer approached.

The fighters had smuggled weapons under their tunics into the Qalai Janghi fortress and tried to fight their way out, Pentagon spokesman Lt. Col. Dan Stoneking said. The Pentagon estimated that fighters numbered 300 the northern alliance had said previously there were 700 prisoners in the facility.

Yahsaw, a spokesman for northern alliance commander Mohammed Mohaqik, said the prisoners broke down doors, seized weapons and ammunition, and fought a pitched battle with guards that lasted some seven hours.

An Associated Press reporter entering the city yesterday evening heard explosions coming from the direction of the fortress. Stoneking, the Pentagon spokesman, confirmed that U.S. airstrikes had helped Gen. Rashid Dostum"s forces regain control of the prison. Dostum brought in about 500 troops to quash the unrest, he said.

International organizations had voiced worry over the prospect of atrocities involving captured fighters.