The CIA worked closely with Muammar Gaddafi's intelligence services in the rendition of terrorist suspects including Abdel-Hakim Belhaj, the rebel commander in Tripoli, according to documents found in Tripoli.

The documents, found in the offices of the former head of Libyan intelligence Musa Kusa, also show that MI6 gave Gaddafi's regime information on Libyan dissidents living in the UK.

The files, uncovered by Human Rights Watch, provide details of the close relationship between western intelligence services, including MI6 and the CIA, and the ousted dictator's regime.

Two documents from March 2004 appear to be American correspondence to Libyan officials to arrange the rendition of Belhaj, the former leader of the Libyan Islamic Fighting Group, a now-dissolved militant group with links to al-Qaida.

Referring to him by his nom de guerre, Abdullah al-Sadiq, the documents say he will be flown from Kuala Lumpur, Malaysia, to Libya, and asks for Libyan government agents to accompany him. They also request US "access to al-Sadiq for debriefing purposes once he is in your custody".

Belhaj has said he was tortured by CIA agents at a secret prison before being returned to Libya.

"Please be advised that we must be assured that al-Sadiq will be treated humanely and that his human rights will be respected," the document states.

Peter Bouckaert, the emergencies director of Human Rights Watch, called the ties between Washington and Gaddafi's regime "a very dark chapter in American intelligence history, and it remains a stain on the record of the American intelligence services that they cooperated with these very abusive intelligence services".

Jennifer Youngblood, a CIA spokeswoman, declined to comment on any specific allegation related to the documents.

She said: "It can't come as a surprise that the Central Intelligence Agency works with foreign governments to help protect our country from terrorism and other deadly threats. That is exactly what we are expected to do."

The documents referring to MI6 contain communications between British and Libyan security services before the former prime minister Tony Blair's desert tent meeting with Gaddafi in 2004. British officials are said to have helped the Libyan dictator with his speechwriting.

The foreign Secretary, William Hague, told Sky News the had no comment to make on intelligence matters.

But he added: "On the subject of these apparent disclosures, first of all they relate to a period under the previous government so I have no knowledge of those, of what was happening behind the scenes at that time."

The documents emerged as the Ministry of Defence (MoD) disclosed that British forces have so far hit more than 900 targets in the Nato campaign to protect Libyan civilians from the Gaddafi regime.

The latest strikes came during armed reconnaissance patrols around buildings in Bani Walid, where rebels believed Gaddafi may have been hiding.

Among the 910 targets damaged or destroyed since operations began in March were secret police headquarters and command bunkers, the MoD said.