The CIA is no longer operating secret prisons used by the intelligence agency to detain and interrogate terror suspects, and plans to shut all remaining "black site" facilities, the agency's director Leon Panetta says.
Suspects held at the infamous secret prisons were interrogated with harsh techniques that included waterboarding.
Mr Panetta said in a letter to agency employees that he had informed Congress of the CIA's detention policies following an order by President Barack Obama in January banning harsh interrogations and ordering that the secret detention sites be closed.
He said the agency had also discontinued using contract employees to conduct interrogations, a concern of influential congressional members who had called the practice an invitation to abuse.
The now-empty 'black sites' in unidentified countries were used to detain suspects who were captured in the war on terrorism launched by former President George Bush after the September 11 attacks.
The three suspects that the CIA has acknowledged were subjected to waterboarding, a form of simulated drowning widely condemned as a form of torture, at such black sites.
The suspects were accused September 11 plotter Khalid Sheikh Mohammed, and al Qaeda suspects Abu Zubayhda and Abd al-Rahim al-Nishiri.
Mr Panetta said the CIA would continue to question suspects as necessary but would use "a dialogue style of questioning that is fully consistent with the interrogation approaches authorized and listed in the Army Field Manual," which bans harsh techniques.
"CIA officers do not tolerate, and will continue to promptly report, any inappropriate behavior or allegations of abuse. That holds true whether a suspect is in the custody of an American partner or a foreign liaison service," he said.