A detainee at the US prison camp at Guantanamo Bay phoned a global TV network on Tuesday to say that he was severely beaten for refusing to leave his cell.
Chadian Mohammed el-Gharani told al-Jazeera that guards beat him with batons and sprayed him with tear gas.
The US has never allowed journalists to interview Guantanamo prisoners and al-Jazeera did not say how it had managed to speak to Mr Gharani.
US army spokesman Brook DeWalt suggested that Mr Gharani may have used one of his weekly phone calls to his family to speak to al-Jazeera.
Mr Gharani did not give the date of the alleged abuse but said it had occurred after the election of US President Barack Obama.
The prisoner says he refused to leave his cell because he was not being permitted to interact with other detainees and was denied 'normal food.'
He said that a group of six soldiers in protective gear had forcibly removed him from the cell and beat him, breaking one of his front teeth.
A US judge ruled in January that Mr Gharani should be freed, dismissing the military's allegations that he was part of al-Qaida and had worked for the Taliban in Afghanistan.
Mr Gharani is being held in a section of the camp where prisoners are permitted 'privileges' while he awaits release