An independent U.N. human rights investigator said on Wednesday that he had information about an inmate being tortured at the U.S. Guantanamo Bay detention facility, despite Washington banning "enhanced interrogation techniques" almost 10 years ago.

The U.S. Department of Defense denied the allegation, saying there was no credible evidence to support it.

Nils Melzer, the U.N. special rapporteur on torture, said he had information that Ammar al-Baluchi — accused of being a co-conspirator in the 9/11 attacks on the United States — was being subjected to treatment that is banned under international law.