Three more terror suspects have attempted suicide at the U.S. detention center in Cuba in the past week, lifting the total to 19, the Pentagon said Wednesday.

There are about 650 detainees at the U.S. Naval base in Cuba, and all are accused of having links to Afghanistan's Taliban regime or Al Qaeda, though none has been charged with a crime.

The three prisoners were treated at the base hospital and are back in their cells, said Pentagon spokeswoman Navy Lt. Cmdr. Barbara Burfeind said. She declined any further details.

Nine attempts have occurred in just six weeks while 10 other attempts occurred over the course of last year.

Burfeind also acknowledged on Wednesday that the United States was transferring some suspects to detention elsewhere, but refused to comment on specific cases or possible other countries involved.

The New York-based Center for Constitutional Rights and the International Human Rights Law Group last week petitioned the Washington-based Inter-American Commission on Human Rights to ensure detainees are not tortured during interrogations and that they not be transferred to third countries, which might tacitly allow torture during questioning.

The groups said some prisoners had been taken to countries including Jordan, Egypt and Morocco for interrogations.

A Mauritanian independent weekly, Le Calame, reported Wednesday that 23 Guantanamo prisoners, including one Mauritanian, had been transferred to a a Moroccan prison for interrogation. The report could not immediately be confirmed, and the newspaper cited no sources.

"From time to time the transfer and release of detainees will occur without notice or mention," Burfeind said.

Amnesty International has demanded an inquiry into whether U.S. interrogations methods were contributing to the suicide attempts. U.S. officials insist the questioning is humane.

A man who tried to hang himself on Jan. 16 is still hospitalized in serious condition. The prospects for his recovery were "still uncertain," Burfiend said, declining further details.

"He is breathing on his own but his level of recovery remains uncertain," she said. The Pentagon has refused to detail the man's injuries, but said his home government and family had been notified.

It was unclear whether the man suffered any brain damage from the attempt, or whether he was conscious.

"Does one of these prisoners have to die in U.S. custody before a full public investigation is conducted?" Amnesty spokesman Alistair Hodgett said in Washington.

The only independent group with steady access to the detainees has been the International Committee of the Red Cross, but it has not been allowed in for interrogations and no longer has a permanent presence on the base.