KABUL, Afghanistan (AP) _ Government troops held off rebels trying to close in on Kabul today as thousands of civilians fled the besieged Afghan capital, some hanging out of packed buses and riding on the roofs.

Hundreds of fighters were reported killed, but conflicting casualty claims could not immediately be verified.

Troops loyal to President Burhanuddin Rabbani were fighting Taliban rebels on the city's eastern fringe. Government jets and helicopter gunships bombed rebel positions Wednesday night and this morning, a government spokesman said.

People thronged markets in central Kabul to stock up on food and essentials, fearing that combat will soon reach the streets of a city that has been hammered for years by rocket attacks.

The rebels, who want to establish a strict Islamic government, reported capturing a military college, about six miles from the presidential palace in the city center.

But the government said its troops had halted the rebels on the outskirts of Kabul, and the fighting was still going on in the Pul-e-Charkhi suburb.

``Fresh troops have been deployed to all front lines of Kabul and many Kabulis have volunteered to take guns and defend their city,'' said Amrullah, the government spokesman.

Pul-e-Charkhi was strewn with bodies of Taliban fighters, he said. The government claimed to have killed 150 rebels, while three of their soldiers were killed and 21 wounded.

But a Taliban spokesman said 100 government soldiers were killed in the battle for the military college.

As government jets returning from bombing raids screamed over Baghram air base, hundreds of jeeps ferried international aid workers to the airport and buses of Afghan civilians headed north to safer areas.

Most Western aid agencies asked their staff to evacuate as the fighting drew closer to Kabul.

``Basically, the city is cornered in all four sides,'' said Esther Robertson of the British group, CARE. ``We feel that it is better to go now while we have a chance.''

The rebels began their advance on the capital Wednesday after capturing the town of Sarobi. Government jets responded with bombing runs as Rabbani's troops desperately tried to hold onto what little of the country they still controlled.

The Taliban, which wants to establish a regime ruled by the Islamic codes laid down in the Koran, now controls about two-thirds of the country. Rabbani holds only Kabul and a few provinces to the north.

In southern Kandahar, Mullah Omar, the Taliban's top commander, announced a general amnesty for anyone who surrendered, including Rabbani.

The Taliban rebels have been advancing steadily since their stunning victory two weeks ago in the eastern city of Jalalabad. They marched to within a few miles of Kabul last year, but were pushed out by government troops a week later.

The Taliban are religious students who broke from other Afghan factions they claimed were riddled with corruption. The rebel groups had united in 1992 to oust the Moscow-backed communist government.

The U.N. Security Council on Wednesday called for an immediate cease-fire in Afghanistan.

There was no reaction from the fighting factions.