ASHINGTON, Dec. 17 — Saddam Hussein is now prisoner No. 1 in what has developed into a global detention system run by the Pentagon and the Central Intelligence Agency, according to government officials.
It is a secretive universe, they said, made up of large and small facilities scattered throughout the world that have sprouted up to handle the hundreds of suspected terrorists of Al Qaeda, Taliban warlords and former officials of the Iraqi government arrested by the United States and its allies since the Sept. 11 attacks on the World Trade Center and the Pentagon and the war in Iraq.
Many of the prisoners are still being held in a network of detention centers ranging from Afghanistan to the United States Naval Base at Guantánamo Bay in Cuba. Officials described it as a prison system with its own unique hierarchy, one in which the most important captives are kept at the greatest distance from the prying eyes of the public and the media. It is a system in which the jailers have refined the arts of interrogation in order to drain the detainees of crucial information.
Mr. Hussein's new address is still a closely guarded secret, although he is still inside Iraq, American officials said Wednesday. No one will say precisely where, but it seems likely that he is at a highly secure detention facility established at Baghdad International Airport, where the United States is holding the other top Iraqi leaders it has captured. When asked if Mr. Hussein was at airport, American officials declined to comment.
The C.I.A. has quietly established its own detention system to handle especially important prisoners. The most important Qaeda leaders are held in small groups in undisclosed locations in friendly countries in the developing world, where they face long interrogations with no promise of ever gaining release. For example, at least two of the top Qaeda figures captured since the Sept. 11 attacks — Abu Zubaydah and Ramzi bin al-Shibh — were held for a time in a secure location in Thailand. They were later moved to another country, officials said.
C.I.A. officials refuse to say precisely how many Qaeda operatives the agency has in detention, but they say about 75 percent of the top two dozen Qaeda leaders in place at the time of the Sept. 11 attacks have been killed or captured. That suggests the agency's detention capacity is far smaller than the large system established by the Pentagon.
In dealing with its captives, the C.I.A. has the advantage of almost complete isolation. Officials say that allows the agency's interrogators to alter the physical surroundings of the Qaeda detainees to try to disorient them and also convince them that they are being held by Arab security services feared for their use of torture. Guards are sometimes dressed in the uniforms of the native countries of the detainees, a technique that may be particularly effective on captives who have experienced jail time back home. Officials said the C.I.A. might not be able to use the full range of interrogation techniques on Mr. Hussein that have been employed with Qaeda leaders. Unlike Qaeda operatives, Mr. Hussein seems destined to face some sort of public judicial review, either through an international war crimes tribunal or other trial, and so the agency's handling of him may eventually come under scrutiny.
Pentagon and C.I.A. officials have denied that they use torture against detainees captured in either Iraq or the wider campaign against terror. The agency's officials have declined to comment on the techniques they use with detainees, but a senior Pentagon official said Wednesday that interrogations conducted by the Pentagon followed "well-established techniques" that do not violate the human rights of the detainees.
Certain techniques that interrogators may wish to apply to elicit information from important detainees require "a higher level of scrutiny" by officials before they can be used, the Pentagon official said.
One military officer said the use of sleep deprivation, for example, must be approved by senior Pentagon officials.
American military officials said Wednesday that 38 of the 55 most wanted Iraqi leaders had either been killed or captured, and several hundred lower-level government officials and Baath Party operatives are also being held. While the most senior officials captured are being held at the Baghdad Airport, many of the lower-level Iraqis are now in Abu Gharib prison west of Baghdad, which was infamous as a torture den under Mr. Hussein's rule but has since been refurbished by American forces. Smaller, regional facilities have also been set up around Iraq temporarily to handle Iraqis caught up in street-level military operations intended to stem the insurgency.
In Afghanistan, meanwhile, the United States military is running a large detention center at Bagram Air Base, where Taliban, Qaeda and other foreign fighters caught in the country are held and questioned. Smaller, short-term detention centers have also been run in both Kandahar and Kabul.
Many of those caught in Afghanistan were eventually flown to Guantánamo, which has become the best-known prison in the global campaign against terror. Guantánamo now holds about 660 prisoners, although that number is expected to decline as some of them are turned over to their home countries.
Still, Guantánamo's inmates are among the least significant of any detainees captured since the Sept. 11 attacks, according to several American counterterrorism experts. The C.I.A. has not sent any of the highest-ranking Qaeda leaders it has captured to the base, officials said.
A final category of detainees are those Qaeda operatives who really are being held by Arab countries, like Egypt, which then provide debriefing reports to the United States.