The American Civil Liberties Union (ACLU) says the intelligence agency has broken both US and international law.

It is acting for a man allegedly flown to a secret CIA prison in Afghanistan.

US Secretary of State Condoleezza Rice says she'll comment on recent reports of alleged CIA prisons abroad before starting a visit to Europe on Monday.

Ms Rice has said she will provide an answer to a EU letter expressing concern over reports last month alleging the US intelligence agency was using secret jails - particularly in eastern Europe.

'Extraordinary rendition'

"The lawsuit will charge that CIA officials at the highest level violated US and universal human rights laws when they authorised agents to abduct an innocent man, detain him incommunicado, beat him, drug and transport him to a secret CIA prison in Afghanistan," the ACLU said in a news release.

The release identified the jail as the "Salt Pit".

The group did not provide the name or nationality of the plaintiff, saying only that he would appear at a news conference next week to reveal details of the lawsuit.

The ACLU also wants to name corporations which it accuses of owning and operating the aircraft used to transport detainees secretly from country to country.

The highly secretive process is known as "extraordinary rendition" whereby intelligence agencies move and interrogate terrorism suspects outside the US, where they have no American legal protection.

It has become extremely controversial, the BBC's Adam Brookes in Washington reports.

Some individuals have claimed they were flown by the CIA to countries like Syria and Egypt, where they were tortured.

The US government and its intelligence agencies maintain that all their operations are conducted within the law and they will no doubt fight this case vigorously, our correspondent says.

He says they will not want to see US intelligence officers forced publicly to defend their actions and they will not want to see one of their most secret procedures laid bare in open court.