WASHINGTON (Reuters) - The CIA used a widely condemned interrogation technique known as waterboarding on three suspects captured after the September 11 attacks, CIA Director Michael Hayden told Congress on Tuesday.

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“Waterboarding has been used on only three detainees,” Hayden told the Senate Intelligence Committee. It was the first time a U.S. official publicly specified the number of people subjected to waterboarding and named them.

Critics call waterboarding a form of illegal torture. Congress is considering banning the technique.

Those subjected to waterboarding were suspected September 11 mastermind Khalid Sheikh Mohammed and senior al Qaeda leaders Abu Zubaydah and Abd al-Rahim al-Nashiri, Hayden said at the hearing on threats to the United States.

He said waterboarding has not been used in five years.

“The circumstances are different than they were in late 2001, early 2002,” Hayden said. “Very critical to those circumstances was the belief that additional catastrophic attacks against the homeland were imminent. In addition to that, my agency ... had limited knowledge about al Qaeda and its workings. Those two realities have changed.”

Hayden told reporters later that the interrogations of Mohammed and Zubaydah were particularly fruitful.

From the time of their capture in 2002 and 2003 until they were delivered to Guantanamo Bay prison in 2006, the two suspects accounted for one-fourth of the human intelligence reports on al Qaeda, Hayden said.

Some analysts have questioned Mohammed’s credibility under interrogation. But Hayden said most of the information was reliable and helped lead to other al Qaeda suspects.

He told the committee he opposed limiting the CIA to using interrogation techniques permitted in the U.S. Army Field Manual, which bans waterboarding. CIA interrogators are better trained, and the agency works with a narrower range of suspects in its interrogations, he said.

HARSH TACTICS

Hayden said fewer than 100 people had been held in the CIA’s terrorism detention and interrogation program launched after the September 11 attacks, with fewer than one-third of them subjected to any harsh interrogation techniques.

But applying the field manual’s limitations to the CIA, he said, “would substantially increase the danger to America.”

The CIA is the only U.S. agency that uses harsh interrogation techniques, National Intelligence Director Michael McConnell told the hearing. The entire military adheres to the Army Field Manual and FBI Director Robert Mueller told the hearing his agency does not use coercive techniques.

A senior intelligence official said after the hearing that it was unclear whether the CIA could legally use waterboarding in the future, given changes in U.S. law. The Bush administration says it neither uses nor condones torture.

The CIA said in December that it had destroyed videotapes depicting the interrogations of Zubaydah and Nashiri, prompting a Justice Department investigation.