WASHINGTON, Dec 21: Detainees at the US military prison at Guantanamo Bay, Cuba, were shackled to the floor in fetal positions for more than 24 hours at a time, left without food and water, and made to urinate and defecate on themselves , says an FBI memo published on Tuesday.

The memo is part of a set of documents released by the American Civil Liberties Union in connection with a lawsuit accusing the US government of being complicit in torture at the Guantanamo Bay prison camp.

The documents cover a two-year period that ended in August and contains memos written by FBI agents and officials who visited or worked at the prison. In the memos, FBI agents report witnessing the use of growling dogs to intimidate detainees, contrary to the Pentagon's claim that it had banned the use of dogs for intimidation after similar abuses at Iraq's Abu Ghraib prison were reported earlier.

One FBI agent reported that he saw a detainee wrapped in an Israeli flag and bombarded with loud music in an attempt to soften his resistance to interrogation. Another set of documents quotes FBI agents witnessing similar abuses at US prisons in Iraq where they reported seeing military personnel beating and choking detainees and placing lighted cigarettes in their ears.

An agent wrote that in one case a detainee who was nearly unconscious had pulled out much of his hair during the night. One of the memorandums was addressed to FBI director Robert Mueller and other senior bureau officials, and it provided the account of someone "who observed serious physical abuses of civilian detainees" in Iraq.

The memorandum, dated June 24 this year, was an "Urgent Report," meaning that the sender regarded it as a priority. It said the witness had "described that such abuses included strangulation, beatings, placement of lit cigarettes into the detainees' ear openings and unauthorized interrogations."

The memorandum said the wit ness, who was not identified as an agent or an informer, had also asserted that there had been an effort to cover up these abuses. The documents also include claims that some military interrogators had posed as FBI officials while using harsh tactics on detainees, both in Iraq and at Guantanamo Bay.

In one memorandum, dated Dec. 5, 2003, an agent whose name is blanked out wrote: "If this detainee is ever released or his story made public in any way, military interrogators will not be held accountable because these torture techniques were done by FBI interrogators," the agent wrote. "The FBI will be left holding the bag before the public."

Another message sent to FBI officials including Valerie Caproni, the bureau's top lawyer, recounted witnessing detainees chained in interrogation rooms at Guantanamo, where about 550 prisoners are being held in a detention camp on the edge of a naval base.

The agent whose name was deleted from the document, wrote on July 29: "On a couple of occasions, I entered interview rooms to find a detainee chained hand and foot in a fetal position to the floor, with no chair, food or water.

Most times they had urinated or defecated on themselves and had been left there for 18 to 24 hours or more." The agent said that on another occasion, the air conditioning had been turned up so high that a chained detainee was shivering.