The 30 shackled prisoners were seen being loaded into buses shortly after disembarking from the aircraft, which had flown with tight security on board from the southern Afghan city of Kandahar.

They join a first group of prisoners, also captives from the US campaign against Afghanistan, who had arrived in the Camp X-Ray detention centre at Guantanamo Bay on Friday.

At a Pentagon news conference, spokeswoman Victoria Clarke insisted that the prisoners were "receiving humane treatment" - including being fed "culturally appropriate" meals.

Imprisoned in cells measuring 1.8 by 2.4 metres (six feet by eight feet), they were also being given the opportunity to exercise daily, she said.

Western captives

As the military camp at Guantanamo Bay does not fall within American sovereign territory, the prisoners have no legal rights under the US constitution, and no right of appeal to federal courts.

The prisoners were taken by bus and ferry to the detention centre

The US defence secretary has maintained that they are "unlawful combatants" rather than prisoners-of-war, an assertion which could have further implications for the rights they are entitled to.

The International Red Cross (ICRC) says it regards the detainees as prisoners-of-war with full rights under the Geneva convention and that it plans to start visiting them early next week.

None of the prisoners has yet been charged but some could face trial in a military court authorised by President George W Bush following the 11 September terror attacks on America.

'No let-up'

In Afghanistan, US warplanes have meanwhile continued to bomb cave complexes in the east of the country around the clock in a bid to destroy surviving Taleban forces and their al-Qaeda terror network allies.

"The idea is to completely render this infrastructure unusable

Lieutenant Colonel Martin Compton Pentagon spokesman

After heavy overnight strikes, they were back in the air on Monday to target the Zhawar region, in the mountainous province of Paktia bordering Pakistan.

The Afghan Islamic Press (AIP), a private news agency based in Pakistan, said there had been "no let-up" in the air strikes over 48 hours.

The US military believes the Zhawar region is being used by fugitives from Afghanistan's former Taleban regime and members of Osama Bin Laden's al-Qaeda network as a staging-post on the way to Pakistan.

According to AIP, US ground troops were also seen near the caves recently, while air strikes have continued against the region for about two weeks.

"The idea is to completely render this infrastructure unusable," a Pentagon spokesman, Lieutenant Colonel Martin Compton, said at the war HQ in Tampa, Florida.

But the US strikes also appear to have claimed civilian lives.

The Associated Press news agency quoted one eyewitness as saying 15 people were killed in his village, about three kilometres from the caves, on Friday.

"No one is left but the dead," said Noorz Ali after fleeing from the region.

"It began at 9pm. There were so many bombs and rockets I couldn't count. In my village, maybe 15 bombs fell."