WASHINGTON - Private security guards from Blackwater Worldwide participated in some of the C.I.A.'s most sensitive activities - clandestine raids with agency officers against people suspected of being insurgents in Iraq and Afghanistan and the transporting of detainees, according to former company employees and intelligence officials.
The raids against suspects occurred on an almost nightly basis during the height of the Iraqi insurgency from 2004 to 2006, with Blackwater personnel playing central roles in what company insiders called "snatch and grab" operations, the former employees and current and former intelligence officers said.
Several former Blackwater guards said that their involvement in the operations became so routine that the lines supposedly dividing the Central Intelligence Agency, the military and Blackwater became blurred. Instead of simply providing security for C.I.A. officers, they say, Blackwater personnel at times became partners in missions to capture or kill militants in Iraq and Afghanistan, a practice that raises questions about the use of guns for hire on the battlefield.
Separately, former Blackwater employees said they helped provide security on some C.I.A. flights transporting detainees in the years after the 2001 terror attacks in the United States.
The secret missions illuminate a far deeper relationship between the spy agency and the private security company than government officials had acknowledged. Blackwater's partnership with the C.I.A. has been enormously profitable for the North Carolina-based company, and became even closer after several top agency officials joined Blackwater.
"It became a very brotherly relationship," said one former top C.I.A. officer. "There was a feeling that Blackwater eventually became an extension of the agency."
George Little, a C.I.A. spokesman, would not comment on Blackwater's ties to the agency. But he said the C.I.A. employs contractors to "enhance the skills of our own work force, just as American law permits."
"Contractors give you flexibility in shaping and managing your talent mix - especially in the short term - but the accountability's still yours," he said.
Mark Corallo, a spokesman for Blackwater, said Thursday that it was never under contract to participate in clandestine raids with the C.I.A. or with Special Operations personnel in Iraq, Afghanistan or anywhere else.
Blackwater's role in the secret operations raises concerns about the extent to which private security companies, hired for defensive guard duty, have joined in offensive military and intelligence operations.
Representative Rush D. Holt, a New Jersey Democrat who is chairman of the House Select Intelligence Oversight Panel, said in an interview that "the use of contractors in intelligence and paramilitary operations is a scandal waiting to be examined." While he declined to comment on specific operations, Mr. Holt said that the use of contractors in such operations "got way out of hand." He added, "It's been very troubling to a lot of people."
Blackwater, now known as Xe Services, has come under intense criticism for what Iraqis have described as reckless conduct by its security guards, and the company lost its lucrative State Department contract to provide diplomatic security for the United States Embassy in Baghdad earlier this year after a 2007 shooting that left 17 Iraqi civilians dead.
Blackwater's ties to the C.I.A. have emerged in recent months, beginning with disclosures in The New York Times that the agency had hired the company as part of a program to assassinate leaders of Al Qaeda and to assist in the C.I.A.'s Predator drone program in Afghanistan and Pakistan.
Leon E. Panetta, the C.I.A. director, recently initiated an internal review examining all Blackwater contracts with the agency to ensure that the company was performing no missions that were "operational in nature," according to one government official.
Five former Blackwater employees and four current and former American intelligence officials interviewed for this article would speak only on condition of anonymity because Blackwater's activities for the agency were secret and former employees feared repercussions from the company. The Blackwater employees said they participated in the raids or had direct knowledge of them.
Along with the former officials, they provided few details about the targets of the raids in Iraq and Afghanistan, although they said that many of the Iraq raids were directed against members of Al Qaeda in Mesopotamia. To corroborate the claims of the company's involvement, a former Blackwater security guard provided photographs to The Times that he said he took during the raids. They showed detainees and armed men whom he and a former company official identified as Blackwater employees. The former intelligence officials said that Blackwater's work with the C.I.A. in Iraq and Afghanistan had grown out of its early contracts with the spy agency to provide security for the C.I.A. stations in both countries.
In the spring of 2002, Erik Prince, the founder of Blackwater, offered to help the spy agency guard its makeshift Afghan station in the Ariana Hotel in Kabul. Not long after Mr. Prince signed the security contract with Alvin B. Krongard, then the C.I.A.'s third-ranking official, dozens of Blackwater personnel - many of them former members of units of the Navy Seals or Army Delta Force - were sent to provide perimeter security for the C.I.A. station.
But the company's role soon changed as Blackwater operatives began accompanying C.I.A. case officers on missions, according to former employees and intelligence officials.
A similar progression happened in Iraq, where Blackwater was first hired for "static security" of the Baghdad station. In addition, Blackwater was charged with providing personal security for C.I.A. officers wherever they traveled in the two countries. That meant that Blackwater personnel accompanied the officers even on offensive operations sometimes begun in conjunction with Delta Force or Navy Seals teams.
A former senior C.I.A. official said that Blackwater's role expanded in 2005 as the Iraqi insurgency intensified. Fearful of the death or capture of one of its officers, the agency banned officers from leaving the Green Zone in Baghdad without security escorts, the official said.
That gave Blackwater greater influence over C.I.A. clandestine operations, since company personnel helped decide the safest way to conduct the missions.
The former American intelligence officials said that Blackwater guards were supposed to only provide perimeter security during raids, leaving it up to C.I.A. officers and Special Operations military personnel to capture or kill suspected insurgents or other targets.
"They were supposed to be the outer layer of the onion, out on the perimeter," said one former Blackwater official of the security guards. Instead, "they were the drivers and the gunslingers," said one former intelligence official.
But in the chaos of the operations, the roles of Blackwater, C.I.A., and military personnel sometimes merged. Former C.I.A. officials said that Blackwater guards often appeared eager to get directly involved in the operations. Experts said that the C.I.A.'s use of contractors in clandestine operations falls into a legal gray area because of the vagueness of language laying out what tasks only government employees may perform.
P.W. Singer, an expert in contracting at the Brookings Institution, said that the types of jobs that have been outsourced in recent years make a mockery of regulations about "inherently governmental" functions.
"We keep finding functions that have been outsourced that common sense, let alone U.S. government policy, would argue should not have been handed over to a private company," he said. "And yet we do it again, and again, and again."
According to one former Blackwater manager, the company's involvement with the C.I.A. raids was "widely known" by Blackwater executives. "It was virtually continuous, and hundreds of guys were involved, rotating in and out," over a period of several years, the former Blackwater manager said.
One former Blackwater guard recalled a meeting in Baghdad in 2004 in which Erik Prince addressed a group of Blackwater guards working with the C.I.A. At the meeting in an air hangar used by Blackwater, the guard said, Mr. Prince encouraged the Blackwater personnel "to do whatever it takes" to help the C.I.A. with the intensifying insurgency, the former guard recalled.
But it is not clear whether top C.I.A. officials in Washington knew or approved of the involvement by Blackwater officials in raids or whether only lower-level officials in Baghdad were aware of what happened on the ground.
The new details of Blackwater's involvement in Iraq come at a time when the House Intelligence Committee is investigating the company's role in the C.I.A.'s assassination program, and a federal grand jury in North Carolina is investigating a wide range of allegations of illegal activity by Blackwater and its personnel, including gun running to Iraq.
Several former Blackwater personnel said that Blackwater guards involved in the C.I.A. raids used weapons, including sawed-off M-4 automatic weapons with silencers, that were not approved for use by private contractors. In separate interviews, former Blackwater security personnel also said they were handpicked by senior Blackwater officials on several occasions to participate in secret flights transporting detainees around war zones.
They said that during the flights, teams of about 10 Blackwater personnel provided security over the detainees.
"A group of individuals were selected who could manage detainees without the use of lethal force," said one former Blackwater guard who participated in one of the flights.
Intelligence officials deny that the agency has ever used Blackwater to fly high-value detainees in and out of secret C.I.A. prisons that were shut down earlier this year. Mr. Corallo, the Blackwater spokesman, said that company personnel were never involved in C.I.A. "rendition flights," which transferred terrorism suspects to other countries for interrogation.