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

The secret report strong implies that the United States violated international law prohibiting torture and maltreatment of prisoners, the newspaper said.

The Washington Post said the ICRC findings were based on its access to the CIA's 14 "high-value" detainees after they were transferred in 2006 to the US detention camp at Guantanamo Bay, Cuba.

The ICRC report gave uniform accounts of abuse that included beatings, sleep deprivation, extreme temperatures and, in some cases, waterboarding, or simulating drowning, the Post said.

The Washington Post said at least five copies of the report were shared with the CIA and top White House officials in 2007.

The newspaper said a copy of the report was obtained by Mark Danner, a journalism professor who published extensive excerpts in the April 9 edition of the New York Review of Books, released on Sunday.

"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.

The report said Danner did not say how he obtained the report.

Many of the details of alleged mistreatment had 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, the newspaper said. It quoted as US official familiar with the ICRC document as saying: "It is important to bear in mind that the report lays out claims made by the terrorists themselves." The CIA could not immediately be reached for comment by Reuters.

Former US President George W. Bush acknowledged the use of coercive interrogation tactics on senior al-Qaeda captives detained by the CIA in the aftermath of the September 11, 2001, attacks. Bush certified in 2007 that the CIA's interrogation program complied with the Geneva Conventions.