A U.S.-based human rights group says at least 11 al-Qaida suspects have "disappeared" in U.S. custody, and that some may have been tortured.
In a new report, Human Rights Watch says the prisoners are being held at secret locations with no access to their families or the International Committee of the Red Cross.
The report says the prisoners include Khalid Shaikh Mohammed, alleged mastermind of the September 11, 2001 terrorist attacks and Abu Zubayda, a suspected close aide of Osama bin Laden.
Human Rights Watch says the use of what it called "forced disappearances" violates international law and the principles of a free society.
U.S. officials have yet to comment on the report. In the past, U.S. officials have said al-Qaida prisoners provided intelligence that helped foil planned terrorist attacks.