Top US counterintelligence officials warned that a concerning number of CIA informants were being captured and executed, according to The New York Times.

The warning came in a top secret memo the officials issued to all of the CIA's stations and bases around the world last week, the Times reported, citing people familiar with the matter.

According to the memo, the agency’s counterintelligence mission center looked at dozens of cases in the last several years involving foreign informants who had been killed, arrested or most likely compromised.

The cable itself was not necessarily unique, but the Times notes announcing the specific number of killings is rare as the information is usually kept strictly underwraps by intelligence officials.

Recruiting spies has always been highly risky, however, the cable warned that the CIA has not excelled in the area recently for reasons that include being too trusting of sources, underestimating foreign intelligence agencies, and moving too quickly to recruit informants while ignoring potential risks, according to the Times.

The uptick in compromised informants highlights 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 report says.

Sometimes, informants discovered by other intelligence services are not arrested, but instead are turned into double agents who feed disinformation to the CIA, according to the memo.

The New York Times also reported that CIA case officers were sometimes promoted for recruiting spies often regardless of the success, performance or quality of that spy.

'No one at the end of the day is being held responsible when things go south with an agent,” Douglas London, a former CIA operative who was unaware of the cable, said to the Times.

'Sometimes there are things beyond our control but there are also occasions of sloppiness and neglect and people in senior positions are never held responsible.' Asked about the memo, a CIA spokeswoman declined to comment.