Hunger-striking detainees at the Guantanamo detention facility are being force-fed through tubes inserted into their noses twice a day -- causing them to gag for air and vomit -- during a procedure that a U.S. military defense lawyer just returned from the U.S. base in Cuba described as “brutal” and agonizing.

Lt. Col. Barry Wingard, who represents two Kuwaiti detainees at Guantanamo, told NBC News on Sunday that one of his clients described being shackled by his wrists and around his waist —while food is “dumped into this throat” for up to two hours at a time. His comments came as the U.S. military released new photos showing the chair to which hunger-striking detainees are strapped, and bottles of Ensure, the nutritional supplement, that they are being fed.

“When that tube goes up your nose, your eyes begin to water, as it passes through the back of your skull. As it passes through your throat, you begin to gag and you begin to suck for air until it's passed into your stomach,” Wingard said. “It’s agony, according to my client.

“The more times that you’ve been force-fed this way, the more your nose gets inflamed, the more your esophagus begins to burn, the more your stomach begins to burn.”

Ronald Flanders, a spokesman for the U.S. Southern Command, said Sunday the force-feeding is a “legally approved procedure” used by the U.S. Bureau of Prisons – and that the technique is similar to that used for the elderly and small children. He also said the procedure is necessary to save lives. “We have an obligation to keep these folks safe,” he said.

The procedure is controversial within the medical community. The American Medical Association recently wrote a letter to Defense Secretary Chuck Hagel saying the force-feeding “violates core ethical values of the medical profession” when a prisoner makes a rational decision to refuse food.

Of the 166 detainees at Guantanamo, 100 are now hunger striking and 23 are being force-fed, according to the U.S. military’s latest figures.

The widening protest last week prompted President Barack Obama to renew his efforts to shutter the prison, used to hold suspected terrorists taken into custody in overseas battlefields. “The idea that we would still maintain forever a group of individuals who have not been tried, that is contrary to who we are, it is contrary to our interests and it needs to stop,” he said.

Congress has so far blocked his efforts, placing restrictions on transferring the detainees to foreign jurisdictions or bringing them into federal prisons in the United States. “The fact is there’s been no coherent plan presented to the Congress of the United States as to how we would dispose of these individuals,” Republican Sen. John McCain said Sunday on Fox News. “And one of them is not to send them back into the fight where they can kill more Americans.”

Wingard, who returned from a five-day trip to Guantanamo last week, said conditions at the facility are “dire and getting worse.” One of his clients, a Kuwaiti named Faiz al-Kandari, has lost a third of his body weight and now weighs 105 pounds but appears determined to continue, he said. Aggravating the situation, 86 detainees have been cleared for release or transfer, but efforts to send them home have stalled, making them more desperate, he said.

As for renewed talk by Obama and others about closing the base, Wingard said, “These men have heard these words for the past eleven and one half years. They’re not going to be brutalized into submission, and I think the net result will be some of them will die.”

New photos released by the U.S. military show how it is dealing with the hunger strike in Guantanamo Bay, NBC's Michael Isikoff reports.

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