The Americans and their Afghan allies appear to be trying to cover up the slaughter of more than 280 foreign Taliban fighters believed to be loyal to Osama bin Laden in Kandahar airport.

Mystery has surrounded the fate of the foreign fighters since the airport was captured last week, after intensive bombing by the Americans. Afghan anti-Taliban forces acknowledged that more than 280 fighters had been holding out in the airport, but claimed that only about 20 were killed. The rest, they claimed, escaped alive.

But one of the Afghan soldiers who took part in the fighting said yesterday that he was ordered to return to the airport a day after it was captured, where he says he helped bury the bodies of about 280 mostly Arab fighters. The soldier, who used the pseudonym Ahmad Gul to protect his identity, said the majority were killed by American bombs.

Two other witnesses, Abdul Basir and Abdul Kadim, said they saw two bulldozers dumping earth into what they believe was a mass grave at the airport.

Two Arab prisoners captured in the fighting – who should be protected under the Geneva conventions – also seem to have disappeared. Mr Gul said he handed over two ethnic Arab prisoners-of-war he helped to capture to some Americans, presumably members of the CIA, who interrogated them on the spot, then took them away. There has been no word on them since.

Reporters were allowed into the airport for the first time yesterday. More than 200 US Marines are setting up a forward base inside, and dozens of armoured troop carriers were parked around the complex. A US Marine captain gave photographers a guided tour.

The airport was devastated in the fighting. Huge craters lay in the runway, and almost all the windows in the modernist terminal building had been smashed, broken glass crunched under our feet.

But not included in the guided tour was the grave site, a short distance away, where Mr Gul said he helped to bury the foreign fighters. The Americans have sealed off the entire airport site, making it impossible to reach the alleged grave.

Mr Gul said he was one of a small group of Afghan soldiers who were sent back to the airport the day after the end of the fighting there to help bury the bodies. He said that on the day he arrived, last Saturday, the soldiers collected about 30 bodies. The next day, he said, they collected as many as 250.

Mr Gul's version of events would strengthen the argument of those who say the Americans prefer to kill the foreign fighters rather than take them alive.

It comes after the massacre at Mazar-i-Sharif, where American and British forces fighting alongside the Northern Alliance killed more than 150 foreign Taliban prisoners-of-war, when they quelled a prison rebellion using air strikes.

In Tora Bora, the Americans continued bombing despite an offer from al-Qa'ida fighters to surrender to the United Nations or diplomats from their own countries. The US would only accept an unconditional surrender which was not forthcoming.

The clashes with the foreign fighters around Kandahar started three weeks ago, as Afghan anti-Taliban forces backed by US air strikes attacked Kandahar province. Anti-Taliban soldiers met the foreign fighters at the small town of Takht-e Pul as they advanced north towards Kandahar. The anti-Taliban forces later pushed the foreign Taliban back to the airport, and a nearby al-Qa'ida training camp.

It was at Takht-e Pul that Mr Gul said he helped capture two Arab Taliban fighters. "We saw a car coming and stopped it to search it," he said. "It was full of weapons. The man inside spoke only Arabic and we didn't understand him. He attacked us and we shot and killed him. Then we saw another car coming and we took the two men inside prisoner. We took them to the Americans. They interrogated them in Arabic, then they took them away. I have not seen them since."

Several Afghan soldiers in Kandahar agreed that the Americans had taken away two Arab Taliban prisoners. But David Romley, a US Marine captain at the airport yesterday, claimed that American forces in Afghanistan were holding only one "battlefield detainee": John Walker, the American Talib who survived the massacre at Mazar. The two Arabs have disappeared.

After a while, Mr Gul said, the anti-Taliban forces pushed the foreign fighters back to the airport. "We would run towards them and attack them, they they would counter-attack, running out towards us," said Mr Gul. "The Americans bombed whenever the fighting flared, but stopped whenever it died down. We offered the Arabs a chance to surrender, but I don't believe they were ready to. When we caught a few, they started fighting us. One even pulled out a grenade and killed himself."

In the end, it seems, almost no prisoners were taken. There are believed to be some foreign Taliban being held in Kandahar prison. It is not clear whether they were fighting at the airport.

The day the fighting ended at the airport, Mr Gul and the other soldiers were ordered to advance into Kandahar city with their commander, Gul Agha, now the governor. On the way, he said, they were attacked by 18 more Taliban fighters who they killed in the road. The international Red Cross was asked to collect and bury some bodies by the roadside. These may have been the ones. But it was Mr Gul and his comrades who were sent back to bury most of the bodies. Mr Gul said: "Most of them had been killed by the bombing. Some had a leg or an arm blown away. A few had been killed by gunshots from our men."

On Saturday, the first day Mr Gul spent collecting the bodies, Mr Basir and Mr Kadim – their real names – passed by on their way to attend the meeting which appointed Mr Agha governor of Kandahar. They stopped at the airport, where they said they saw two bulldozers dumping earth into a large trench that looked like a mass grave. They saw the bodies of two dead foreign Taliban lying by the side or the road.

At the airport yesterday, the US Marines were busy clearing away the debris, and checking the perimeter for mines, setting up the site as a forward base for operations which Captain Romley said he did not "care to characterise".

Meanwhile, the site where Mr Gul claimed more than 280 massacred Taliban were buried lies out of reach.