More than half of the men held at the Guantanamo detention camp have joined an escalating hunger strike to protest their open-ended detention, a camp spokesman has said.

The US military counted 84 of the 166 prisoners as hunger strikers and was force-feeding 16 of them liquid meals through tubes inserted in their noses and down into their stomachs.

Six were hospitalised for observation, Lieutenant Colonel Samuel House, a spokesman for the detention operation at the Guantanamo Bay US Naval Base, said on Monday..

Hunger strikes have occurred at the facility in southeastern Cuba since shortly after the US began detaining suspected al-Qaeda and Taliban captives there in January 2002.

The current hunger strike began in early February, after guards seized photos and other belongings during a cell search. Prisoners said the guards had also mistreated their Qurans during the search, which the US military denies.

Medical reinforcements

House said the US military is sending additional medical personnel to the prison camp as a consequence of the increasing number of detainees on hunger strike.

He said the new arrivals, numbering under 40, would include a doctor, nurses, corpsmen and medics, who will supplement the 100 medical personnel already on duty.

Forty-three prisoners had joined the hunger strike by April 13, when guards in riot gear swept through a communal prison and forced the detainees into one-man cells where they could be better monitored. Camp officials said the detainees had covered the security cameras and windows, blocking guards' view.

The number refusing meals has grown steadily since then, and two prisoners tried to kill themselves by making nooses with their clothing, House said.

Though the cell search was the immediate trigger, military officials and lawyers for the prisoners have said the protest generally reflects frustration with the failure to resolve the inmates' fate. Most have been held for more than a decade without charge or trial and President Barack Obama has blamed Congress for preventing the closure of the prison.

"It's escalated because the men are desperate and they've hit a breaking point," said Carlos Warner, a federal public defender from Ohio who is part of a team representing 11 Guantanamo prisoners.

"Really what is behind all this is the president abandoned his promise to close Guantanamo. The men know that, they're desperate."