WASHINGTON, Dec 7: Agents of the US Federal Bureau of Investigations saw military interrogators use abusive tactics on prisoners at the naval base at Guantanamo Bay, Cuba, officials said on Monday.

The account of incidents in 2002 involving foreign terrorism suspects held at the base was contained in a July letter from FBI counter terrorism official Thomas Harrington to Maj Gen Donald Ryder, the Army's provost marshal, and was confirmed by Pentagon and Justice Department officials.

Mr Harrington, who headed a group of investigators which visited the base, detailed incidents including one in which a prisoner was menaced by a dog and placed into isolation and another in which a detainee's mouth was covered with duct tape.

In his letter, Mr Harrington referred to the incidents as examples of "highly aggressive interrogation techniques" and asked Gen Ryder, the Army's senior criminal investigator, to take "appropriate action". Mr Harrington wrote that the FBI told Pentagon lawyers in January last year about the abusive treatment, but the matter had not been addressed.

"We take all allegations seriously and investigate each one fully," Brig Gen Jay Hood, commander of the Guantanamo prison, said in a statement provided by the US military.

"The appropriate actions were taken, and some allegations are still under investigation. Immediate and appropriate action is always taken upon all verified allegations. Once investigations are completed, we report them immediately up the chain of command," Gen Hood added.

Lt Col Gerard Healy, an Army spokesman at the Pentagon, declined to identify a woman interrogator charged pinpointed in the report as the worst offender, but said the allegations about her conduct were being examined by Army criminal investigators.

The Pentagon has denied that detainees have been tortured at Guantanamo. The US military holds about 550 non-American citizens at the Guantanamo base, nearly all without charges or access to lawyers. Most were caught in Afghanistan and many have been held at the base for nearly three years.

Some men who have been released from the prison have stated they were tortured there. The International Committee of the Red Cross has accused the United States of using tactics "tantamount to torture" on Guantanamo prisoners. -Reuters