WASHINGTON - A leaked Red Cross report on CIA "torture" of detainees offers fresh ammunition to demands that officials from the Bush administration be prosecuted for their conduct, rights groups have revealed.

President Barack Obama has so far sidestepped calls from some fellow Democrats and from civil liberties activists to go after officials from the previous administration over torture allegations, saying he wants to "look forward."

But his administration will face renewed pressure to take action following the leaking of the internal document from the International Committee of the Red Cross (ICRC), which describes abuse in harrowing detail.

"The more these kind of reports come out, the more pressure it puts on the government to do something," said Sarah Mendelson, director of the human rights and security initiative at the Center for Strategic and International Studies.

Providing the most detailed account yet of the treatment of detainees under former president George W. Bush, the 2007 report by the ICRC describes beatings, sleep deprivation, extreme temperatures and "suffocation by water," of 14 suspected Al-Qaeda members.

The abuse described by the detainees, including being slammed into walls and deprived of sleep and solid food for days, "constituted torture," the Red Cross document said.

Other methods "constituted cruel, inhuman or degrading treatment," it said.

The American Civil Liberties Union (ACLU) and the Center for Constitutional Rights have both urged an aggressive investigation of officials who allegedly approved the use of torture, citing revelations in court documents and other sources already made public.

"I think there is enough evidence in the public domain to warrant a much more serious investigation than has been conducted thus far," Jameel Jaffer, director of ACLU's national security program, told AFP.

"And there's certainly enough evidence out there to warrant the appointment of an independent prosecutor to look into criminal responsibility for the torture of prisoners in CIA custody," Jaffer said.

ICRC officials did not dispute the authenticity of the report, but a spokesman at the agency's headquarters in Geneva regretted that the document was made public. The CIA declined to comment.

The report carried added weight given the neutrality of the ICRC, a humanitarian organization that carefully avoids political comment and works to assist those detained or displaced in war.

At least five copies of the report had been shared with the CIA and top White House officials in 2007, but barred from public release by ICRC guidelines intended to preserve the organization's policy of neutrality.

Rights activists speculated the document may have been leaked by officials in the current administration amid internal debates about detention policies.

As a signatory to the UN convention banning torture, the United States may be legally obliged to carry out a probe of former officials, Mendelson said.

"I think they are compelled to open some kind of investigation by allegations of torture, under the convention against torture," she said.

"That investigation does not need to be made public but they need to be doing it."

Some Democrats in Congress have called for a truth commission to look into a range of alleged abuses by the former administration as part of the "war on terror," including CIA interrogations at secret sites and warrantless wiretapping.

Obama has offered a cool reception to calls for truth commissions but has not ruled out possible prosecutions, saying no one should be above the law.

The president said last month that "my general orientation is to say let's get it right moving forward."

Since Obama took office, government departments have released documents that have shed light on how the previous administration carried out controversial policies, such as the transfer of prisoners for secret interrogations.

Republican lawmakers meanwhile have condemned the truth commission proposal as a witch-hunt.

Some critics of the Bush administration say even a truth commission inquiry would be a half-measure.

"This is not about mistakes. This is about fundamental lawbreaking, about the disposal of the Constitution, and about the end of treaties," Michael Ratner, president of the Center for Constitutional Rights, said in a radio interview earlier this month.