Did Russia kill JFK? Long-secret CIA files show a Russian spy's theory.

The U.S. government released Monday a large trove of documents pertaining to the assassination of President John F. Kennedy, including previously top-secret audio files and transcripts of the CIA interrogating a former Soviet spy who claimed to have intimate knowledge about the killer's connection to Moscow.

In accordance with the JFK Assassination Records Collection Act of 1992, which mandates that all5 million pages of JFK-related documents become public by later this year, the CIA and FBI declassified more than 3,800 files and made them available at the National Archive. The batch includes 3,369 items that were previously redacted and 441 never-before-seen items, including a number of CIA interviews with KGB defector Yuri Nosenko.

Nosenko claimed that Kennedy's killer, Lee Harvey Oswald, had been surveilled during a trip to the Soviet Union, but not recruited, and that another KGB defector working with the CIA was really a plant from Moscow. Both ex-KGB spies accused the other of intentionally spreading disinformation on behalf of the USSR, but it was Nosenko who was infamously held for years by the CIA, which suspected him of trying to muddle the testimonies of his former comrade and of shielding inside information of a Soviet plot to kill Kennedy.