Updated

The International Committee of the Red Cross concluded in a secret report that the Bush administration's treatment of Al Qaeda captives in CIA prisons "constituted torture," The Washington Post reported on Monday.

The account of alleged physical and psychological brutality inside CIA prisons overseas also states that some U.S. practices amounted to "cruel, inhuman or degrading treatment," the newspaper reported.

The secret report strongly implies that the United States violated international law prohibiting torture and mistreatment of prisoners, the Post said.

ICRC officials were granted exclusive access to 14 of the CIA's "high-value" detainees after they were transferred in 2006 to Guantanamo Bay. The prisoners, previously kept in isolation, gave detailed accounts of the alleged abuse they endured — including beatings, sleep deprivation, extreme temperatures and waterboarding.

One incident is described by Abu Zubaydah, a Palestinian man who ran Al Qaeda recruitment. Zubaydah said in the weeks after he was captured, he was shackled naked while listening to consistent music or static. He also says he had limited nourishment and was not allowed to sleep.

The ICRC report was shared with the CIA and White House officials in 2007, but was prohibited from public release. It was eventually obtained by journalism professor Mark Danner, who published excepts in the April 9 edition of the New York Review of Books.

"The ill-treatment to which they were subjected while held in the CIA program, either singly or in combination, constituted torture," Danner quoted the report as saying.

Danner did not detail how he obtained the report.

Many of the details of alleged mistreatment have been reported previously, but the ICRC report is the most authoritative account and the first to use the word "torture" in a legal context, The Washington Post said.

The CIA declined to comment to the Washington Post, but a U.S. official familiar with the report said it is important to keep in mind that the report was derived of claims made by the terrorists themselves.

Click here to read the full report from the Washington Post.

Reuters contributed to this report.