KABUL/WASHINGTON - U.S.-backed anti-Taliban fighters entered the Afghan capital Kabul on Tuesday as reports from across the country pointed to a collapse of Taliban rule.

The bulk of the opposition Northern Alliance forces, who have made sweeping gains with backing from U.S. air strikes, remained in position on the outskirts of Kabul.

But witnesses said the alliance's defense and foreign ministers had driven into the city.

In the United States, an airliner crashed in New York after takeoff on Monday, killing all 260 on board and sparking fears -- apparently unfounded -- that America was again under attack.

U.S. transport officials said early information pointed to an accident, possibly involving engine failure.

Dazed Kabul residents, fearful of a return of the alliance following bloody power struggles when they last controlled the city, emerged from their homes to see the occasional body of a Taliban fighter in the street.

"We have taken Kabul," one Northern Alliance fighter shouted as he stood with a group of fellow fighters on a street in the city center.

"We have taken key government buildings," a second fighter told Reuters. "We are chasing the Taliban to the west."

The United States, which went to war against the Taliban and their guest Osama bin Laden following the September 11 attacks on New York and Washington, has urged the alliance to wait for agreement on a broad-based government before entering Kabul.

Many of Afghanistan's Taliban rulers appeared to have slipped away under cover of night, abandoning a city they had held since winning a civil war in the mid-1990s and imposing their own strict interpretation of Islam on the country.

Small-arms fire erupted in parts of the city, apparently coming from Taliban who had not managed to leave or had chosen to make a last stand.

Witnesses reported looting of government buildings.

The traditional stronghold of the Taliban, who emerged from the mujahideen guerrillas who ejected the Soviet Union from Afghanistan, is the southern city of Kandahar but the immediate destination of those who had left Kabul was unclear.

The father of one of eight Western aid workers, held on charges of promoting Christianity, quoted Taliban diplomats in Pakistan as saying that all eight had been taken to Kandahar.

But tribal leaders in Kandahar, quoted by a source across the border in Pakistan, said that forces loyal to the opposition had taken control of the airport there.

Qatar's Al-Jazeera television carried a similar report.

In the west, an anti-Taliban spokesman said that opposition commander Ismail Khan had entered the ancient city of Herat, his former powerbase, with 4,000 fighters at dawn on Tuesday.

The triumphant return of the warlord, after the capture of the city on Monday, came six years after the Taliban ousted him.

The White House said it was studying reports from Kabul. "At this point, the situation on the ground is very fluid," White House National Security Council spokesman Sean McCormack said.

Afghanistan's neighbor, Pakistan, said it was closely watching developments in Kabul.

"Until the setting up of a multi-ethnic dispensation, no single group should occupy Kabul," Aziz Ahmed Khan, Pakistan's Foreign Ministry spokesman, told Reuters.

"We would like Kabul to be a demilitarized zone... and of course we don't want any bloodshed," Khan added.

The whereabouts of bin Laden and his protector, Taliban spiritual leader Mullah Mohammad Omar, were unclear.

The United Nations said on Monday it wanted Afghan politicians to meet within days, make interim arrangements for Kabul and provide the nucleus for a broad-based government to replace the Taliban.

Diplomats at the United Nations said they expected a meeting to take place in Europe, possibly in Geneva or Vienna, but a venue closer to Afghanistan was also possible.

Troops from Muslim countries such as Turkey, Bangladesh and Indonesia could help the Afghan politicians reimpose order in Kabul if the Taliban collapse, but the United Nations would play mainly a supporting role, they added.

The Northern Alliance broke through Taliban lines to the north of Kabul on Monday, following U.S. air strikes on Taliban defenses there.

Alliance Foreign Minister Abdullah Abdullah said on Monday that their intention was not to enter Kabul.

"We should evaluate the situation, we should try our best not to enter Kabul. That should be the focus," he said.

But Abdullah told Reuters at the weekend that alliance forces might enter if there was a power vacuum.

The vehicles of those who were roaming round the center of Kabul on Tuesday were plastered with photographs of their assassinated leader, Ahmad Shah Masood.

Masood was killed in a suicide attack just two days before the September 11 attacks with hijacked airliners, which killed an estimated 4,500 Americans and foreign nationals.

Washington accuses Saudi-born bin Laden of masterminding the attacks.

The Northern Alliance is made up mainly of ethnic Tajiks and Uzbeks. Pakistan is keen to see the a role in any post-Taliban government for the majority Pashtun, from whom the Taliban draw their support.

Pakistan backed the Taliban until the September 11 attacks.

President Bush said he was pleased with the Northern Alliance's advances in northern Afghanistan but he stressed that Kabul should be a "multi-tribal" state.

Speaking before talks on Tuesday with Russian President Vladimir Putin, Bush said he had received detailed advice from the Russian leader on Afghanistan, where the Soviet Union fought and lost a nine-year war that ended in 1989.

Monday's plane crash on a neighborhood in New York shocked a city still reeling from the September 11 attacks but the shockwaves traveled further afield.

On the heels of widespread declines among U.S. and European carriers on Monday, airline shares in China, Japan, Hong Kong, Singapore and Korea fell between one and five percent. Tourism and airplane parts makers were also dragged lower. Nampa/Reuters