Six human rights groups urged the U.S. government on Thursday to name and explain the whereabouts of 39 people they said were believed to have been held in U.S. custody and "disappeared."

The groups, including Amnesty International and Human Rights Watch, said they filed a U.S. federal lawsuit under the Freedom of Information Act seeking information about the 39 people it terms "ghost prisoners" in the U.S. "war on terror."

"Since the end of Latin America's dirty wars, the world has rejected the use of 'disappearances' as a fundamental violation of international law," Professor Meg Satterthwaite of the Center for Human Rights and Global Justice at New York University's School of Law said in a statement.

The report said suspects' relatives, including children as young as seven, had been held in secret detention on occasion.

In September, U.S. President George W. Bush acknowledged the CIA had interrogated dozens of suspects at secret overseas locations and said 14 of those held had been sent to the U.S. military prison at Guantanamo Bay.

Bush strongly defended the secret detention and questioning of terrorism suspects and said the CIA treated them humanely. The program has drawn international outcry and questions about the cooperation of European governments.

Tens of thousands of people "disappeared" during Latin America's so-called dirty wars in Chile, Argentina and several other countries where right-wing dictators used extra-judicial detentions to crush armed Marxist opposition.

The list of 39 people said to have been held in U.S. custody at some point was compiled using information from six rights groups, including London-based groups Cageprisoners and Reprieve and the Center for Constitutional Rights in New York.

The detentions began shortly after the Sept. 11 attacks and include people said to be captured in locations including Iraq, Saudi Arabia, Pakistan, Somalia and Afghanistan.

EVIDENCE OF DETENTIONS

The United States has acknowledged detaining three of the 39. The groups said, however, that there was strong evidence, including witness testimony, of secret detention in 18 more cases and some evidence of secret detention in the remaining 18 cases.

Joanne Mariner of Human Rights Watch said it was unknown if the suspects were now in U.S. or foreign custody, or even alive or dead.

"We have families who have not seen their loved ones for years. They've literally disappeared," Mariner told Reuters.

Among the cases detailed in the report is the detention in September 2002 of two children, then aged seven and nine, of confessed Sept. 11 mastermind Khalid Sheikh Mohammed, who was later detained and is now held at Guantanamo.

"According to eyewitnesses, the two were held in an adult detention center for at least four months while U.S. agents questioned the children about their father's whereabouts."

The groups said the lack of information about the prisoners "prevents scrutiny by the public or the courts, and leaves detainees vulnerable to abuses that include torture."

Bush said in September there were no prisoners remaining in custody in U.S. secret facilities at that time. But the report said the transfer of Abd al-Hadi al-Iraqi from CIA custody to Guantanamo in April showed the system was still operating.

"Interviews with prisoners who have been released from secret CIA prisons indicate that low-level detainees have frequently been arrested far from any battlefield, and held in isolation for years without legal recourse or contact with their families or outside agencies," the report said.

The groups urged the U.S. government to cease use of secret detention, provide information on those in custody, give access by the International Committee of the Red Cross to all detainees and either bring charges or release all prisoners.