US counterintelligence officials are warning CIA stations around the world about "troubling" numbers of informants recruited from other nations to spy for America being captured or killed, according to a media report which said in recent years "adversarial intelligence services" in countries such as Russia, China, Iran and Pakistan have hunted down the agency's sources and turned them into double agents in some cases.

The New York Times said in a report that "top American counterintelligence officials warned every CIA station and base around the world last week about troubling numbers of informants recruited from other countries to spy for the United States being captured or killed."

The message was sent in an unusual top secret cable and said that "the CIA's counterintelligence mission center had looked at dozens of cases in the last several years involving foreign informants who had been killed, arrested or most likely compromised."

The cable also highlighted "the struggle the spy agency is having as it works to recruit spies around the world in difficult operating environments.

In recent years, adversarial intelligence services in countries such as Russia, China, Iran and Pakistan have been hunting down the CIA's sources and in some cases turning them into double agents," the NYT report said on Tuesday.

The report also said that sometimes, informants who are discovered by adversarial intelligence services are not arrested, "but instead are turned into double agents who feed disinformation to the CIA, which can have devastating effects on intelligence collection and analysis. Pakistanis have been particularly effective in this sphere," the report quoted former officials as saying.

"The collapse of the American-backed government in Afghanistan means that learning more about Pakistan's ties to the Taliban government and extremist organisations in the region is going to become ever more important. As a result, the pressure is once again on the CIA to build and maintain networks of informants in Pakistan, a country with a record of discovering and breaking those networks," the NYT report said.

The brief cable had also laid out the specific number of agents executed by rival intelligence agencies, the report said, noting that this was usually a closely held detail that counterintelligence officials typically did not share in such messages.

"Acknowledging that recruiting spies is a high-risk business, the cable raised issues that have plagued the agency in recent years, including poor tradecraft; being too trusting of sources; underestimating foreign intelligence agencies, and moving too quickly to recruit informants while not paying enough attention to potential counterintelligence risks - a problem the cable called placing "mission over security"," the report said.

The report said CIA's assistant director for counterintelligence Sheetal Patel has not been reluctant to send out broad warnings to the CIA community of current and former officers and earlier this year had sent a letter to retired officers of the agency warning against working for foreign governments who are trying to build up spying capabilities by hiring retired intelligence officials.

"The large number of compromised informants in recent years also demonstrated the growing prowess of other countries in employing innovations like biometric scans, facial recognition, artificial intelligence and hacking tools to track the movements of CIA officers in order to discover their sources," the NYT report said.

With the CIA devoting bulk of its attention for the last two decades to terrorist threats and the conflicts in Afghanistan, Iraq and Syria, the report said improving intelligence collection "on adversarial powers, both great and small, is once again a centerpiece of the CIA's agenda, particularly as policymakers demand more insight into China and Russia."