Emaciated and frail, more than 100 men lie on concrete floors of freezing, solitary cells in Guantánamo, silently starving themselves to death.

Stripped of all possessions, even basics such as a sleeping mat or soap, they lie listlessly as guards periodically bang on the steel doors and shout at them to move an arm or leg to prove they are still conscious.

The notorious detention centre is in crisis, suffering a rebellion of unprecedented scale, with most of the camp on lockdown and around two-thirds of the 166 detainees on hunger strike.

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This week 40 American military nurses were drafted in to try to stem a mass suicide. The last Brit inside, Shaker Aamer, has said he is prepared to strike to his death.

The US administration does its best to keep prying eyes from the unfolding tragedy but the The Independent has obtained first-hand reports.

Twice a day, the 23 most weak are taken into a room. Their wrists, arms, stomach, legs and head are strapped to a chair and repeated attempts are made to force a tube down their noses into their stomachs. It is an ugly procedure as they gag and wretch, blood dripping from their nostrils. “They won’t let us live in peace and now they won’t let us die in peace,” said detainee, Fayiz Al-Kandari, a Kuwaiti held for 11 years without charge.

Four are so ill that they lie in shackles in the hospital wing and insiders predict it is only a matter of time before one perishes.

“It is possible that I may die in here,” said Mr Aamer, 44, through his lawyer, Clive Stafford Smith, recently. “I hope not, but if I do die, please tell my children that I loved them above all else, but that I had to stand up for the principle that they cannot just keep holding people without a trial, especially when they have been cleared for release,” said the father of four, who remains in Camp 5 despite being approved for release more than five years ago. “Sad to say, torture and abuse continue in Guantánamo Bay and the US is throwing away yet more of its dwindling moral authority,” added Mr Stafford Smith.

The protest, which began on 6 February, has now spread through Camp 6 and Camp 5 with an estimated 100 to 130 taking part. These are not the high value detainees kept in Camp 7, the handful charged with terror offences. The hunger strikers are those who have waited a decade or more without trial, including 86 cleared for release but remain trapped because of restrictions imposed by Congress.

As President Barack Obama pledged to press for Guantánamo’s closure this week, detainees described how it has gone back to the draconian regime of the Bush administration.

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“Defence lawyers have tried to engage in constructive dialogue but we have been met with resistance and silence,” explained US Army Captain Jason Wright, a lawyer who described seeing his client Obaidullah, now a 115lb “bag of bones” , a few days ago as “extremely distressing”.

“I have pain in waist, dizziness. I cannot sleep well. I fell [sic] hopeless. I cannot exercise. My muscle become weaker in the last 50 days. I have thrown up five times,” wrote Obaidullah, a 32-year-old Afghan who has never been charged despite 11 years imprisonment.

“When I walked into the room he was demonstrably changed. He said, ‘They won’t treat us with dignity, they are treating us like dogs’. There is an urgency. It is clear that if this hunger strike continues there will be deaths. These men are going to die in this prison for nothing. It is an absolute outrage,” said Capt Wright.

“The hunger strike is a political protest. The fact that they are being treated in this manner is contrary to international law and un-American,” he added. The protest began on 6 February when, according to lawyers, the new administration decided to end “an era of permissiveness” and take a more punitive approach, in contravention with the Geneva Convention, which calls for preventative detention. Guards confiscated all “comfort items” but what inflamed inmates most was a search of their Korans, an act the administration denies.

Prisoners began writing SOS on the outside of their cells but the protest passed peacefully until 13 April when guards used rubber bullets to move inmates from communal cell blocks, where they had covered cameras, and some responded with “improvised weapons” such as broom handles.

First-hand reports this week reveal that most prisoners are now being held in solitary confinement in empty, windowless cells just 12ft by 8ft. Clean water is rationed, they say, and they have been stripped off all possessions.

They complain the air-conditioning has been turned up to an icy level, guards deliberately disturb prayer times and turn up throughout the night to take them for showers.

Describing sleeping on a concrete floor, using his shoes as a pillow, Moroccan Younous Chekkouri said via phone to his lawyers at the charity Reprieve: “Pain starts immediately when I’m on the floor. Pain in my neck, pain in my chest. Finally at night they gave us blankets. It was very cold. Water is now a privilege. They are treating us like animals,” he added. “I thought my torture had ended, but what is happening now is horrible.”

Amnesty was among several human rights organisations to describe the situation at the camp in Cuba as “at crisis point” this week while UN special rapporteur on torture Juan Mendez condemned the continued detention as “cruel, inhuman and degrading”.

Omar Deghayes, 43, a British resident who was released without charge in 2007, recalled the effect of two shorter hunger strikes. Lying in a “fridge-like” cell, he said he could barely stand within four days and was consumed with hunger and pains.

“You start to hallucinate. When people talk to you, you can’t understand them. I started to hear voices. Then I started to vomit blood and puss. Your stomach contracts and when they force feed large quantities, you can’t control anything, you get diarrhoea on your trousers. They take you into the yard and hose you down.”

Most people cannot survive losing more than 40 per cent of their body weight. Once fat stores are depleted, the body begins to consume the muscles and vital organs for energy. A large number on the current hunger strike have lost around a third of their body weight. While some are keeping alive by using a vitamin and mineral drink, 23 are now being force-fed.

Lieutenant Colonel Barry Wingard, a lawyer who visited Mr Al-Kandari, this week, explained: “He said they strap you to a chair, tie up your wrists, your legs, your forehead and tightly around the waist. The tube makes his eyes water excessively and blood begins to trickle from the nose. Once the tube passes his throat the gag reflex kicks in. Warm liquid is poured into the body for 45 minutes to two hours. He feels like his body is going to convulse and often vomits.

“He is emaciated, down from 150lb to 100lb. He can’t walk. He finds is difficult to concentrate. He burps all the time as his stomach eats itself,” added the US Air Force officer, who described the treatment as “beyond hypocrisy”.

The Department of Defence said yesterday it used enteral feeding only when a detainee’s life was in danger. Lieutenant Colonel Todd Breasseale added detainees had the highest standards of humane treatment.

“Detainees are not punished for hunger striking. However, we will not allow them to harm themselves,” he said, adding: “We will not allow them to commit suicide by starving themselves to death.”

Prisoners complain, however, that instead of leaving the tube in, they reinsert it twice a day. Dr Jeremy Lazarus, president of the American Medical Association, wrote to Defence Secretary Chuck Hagel recently to complain that force feeding was in violation of medical ethics.

Capt Wright, who travelled on the same plane as the nurses, said this week: “I can’t imagine they understood what they are being asked to do for their country. I don’t think they knew how horrific it would be. I hope some of them have the courage to say no.”