Their claims back similar allegations by two other British detainees.
Asif Iqbal, Ruhal Ahmad and Shafiq Rasul, all from the town of Tipton in central England, said they were regularly mistreated from the moment they were handed over to US forces in Afghanistan in late 2001.
After being taken to a US detention centre in the Afghan city of Kandahar, they were forced to kneel bent forwards for hours with their foreheads touching the ground, Rasul told The Observer newspaper on Sunday.
"I lifted my head up slightly because I was really in pain. The sergeant came up behind me, kicked my legs from underneath me, then knelt on my back," he said.
"They took me outside and searched me while one man was sitting on me, kicking and punching."
The three childhood friends, aged between 22 and 26, said they had gone to Pakistan for Iqbal's planned wedding, arranged by his family, before going into Afghanistan to help arrange humanitarian aid.
There they were captured by the US-backed Northern Alliance and almost died after hundreds of prisoners were forced into lorry containers, the majority of whom suffocated.
The trio's allegations of US mistreatment follow similar claims made earlier this week by two other British returnees.
"Tariq Dergoul condemns the US and UK governments for these gross breaches of human rights and demands the immediate release of all other detainees at Guantanamo Bay"
Tariq Dergoul, a 26-year-old former care worker from east London, said in a statement issued through his lawyer on Friday that he had endured "botched medical treatment, interrogation at gunpoint, beatings and inhuman conditions".
It is believed a failed operation to treat injuries to Dergoul's arm, led to its amputation.
In a statement issued through his solicitor, Louise Christian, Dergoul "condemns the US and UK governments for these gross breaches of human rights and demands the immediate release of all other detainees at Guantanamo Bay."
Earlier that day, another released Briton, 37-year-old website designer Jamal al-Harith, said in a newspaper interview he had experienced beatings and degrading treatment during his two years at the jail.
He told The Mirror how a squad of five US military police attacked him with batons, fists, feet and knives after he refused to receive an injection.
Al-Harith said the squad, from the US military's Extreme Reaction Force, chanted: "Comply, comply. Do not resist. Do not resist," while conducting the attack.
The men were ''shackled for up
to 15 hours and kept in cages''
"They were really gung-ho, hyped up and aggressive," he said.
"The beatings were not nearly as bad as the psychological torture – bruises heal after a week but the other stuff stays with you. The whole point of Guantanamo was to get to you psychologically," al-Harith, a divorced father of three, added.
Rats, snakes and scorpions
Al-Harith also said prisoners were shackled for up to 15 hours at a time in hand and leg cuffs with links that cut into the skin. They were kept in wire cages that were open to the elements, as well as rats, snakes and scorpions, he added.
Force feeding, al-Harith said, was used to end a hunger strike by 70% of the 600 inmates, which began after a guard kicked a copy of the Quran.
He said prisoners were left malnourished by a diet of porridge and fruit. Some food, he said, was 10 years out of date.
Al-Harith also claimed that when carrying out an amputation, US medical staff often removed more of a limb than was necessary.
"The beatings were not nearly as bad as the psychological torture – bruises heal after a week but the other stuff stays with you. The whole point of Guantanamo was to get to you psychologically"
released Camp Delta detainee
He said he knew of 11 men who had legs amputated and two who lost toes and fingers.
"The man in the cell next to me had frostbite in two fingers and two toes. He also had it in his big toe, but they didn't treat that for a year by which time they had to cut off much more than was needed."
In addition to the beatings, al-Harith said the abuse at the camp included US soldiers bringing in prostitutes and parading them naked in front of Muslim prisoners.
US Secretary of State Colin Powell told a British television programme which also interviewed al-Harith that the charges were "unlikely".
The five British men flew home on Tuesday from Camp Delta, the high-security camp in Guantanamo Bay, Cuba, where the US is holding about 800 suspected al-Qaida and Taliban fighters.
Despite their lengthy detention and although four of the men were briefly held by British police when they returned, none has been charged with any crimes.
The three friends recounted being repeatedly interrogated by both US and British intelligence officials who falsely claimed to have incontrovertible evidence linking them to al-Qaida network.
Powell insists detainees are
'illegal combatants' with no rights
They also allege that British diplomats failed to intervene when US forces arrested the men. Instead, they said MI5 officers interrogated them at the US base in Kandahar and, using a handgun held to their heads, tried to force them into making false confessions.
The trio said that last year they were moved to an isolation block at the Cuban camp after interrogators said they had been seen on a video tape made in August 2000 standing behind al-Qaida leader Usama bin Ladin.
Rasul told the newspaper he had pointed out that at the time he was allegedly with bin Ladin, he had been enrolled at a British university and working at a local electrical goods shop - both facts that could be easily checked.
On being told he could have falsified these, Rasul made a false confession along with his friends.
"I got to the point where I just couldn't take it any more. Do what you have to do, I told them.
"The treatment of the Guantanamo detainees is a human rights scandal which violates international law and damages US claims to uphold the rule of law"
"I'd been sitting there for three months in isolation so I said yes, it's me. Go ahead and put me on trial," Rasul said.
Washington insists that those held at the base are "illegal combatants", and thus not subject to rules governing either civilian or military prisoners.
Human rights organisations, including Amnesty International and Human Rights Watch have condemned the treatment of prisoners at Camp Delta.
"The treatment of the Guantanamo detainees is a human rights scandal which violates international law and damages US claims to uphold the rule of law," Amnesty International said in a statement.