Kim Jong Nam, the murdered half-brother of North Korea's Kim Jong Un, was a Central Intelligence Agency source.

The CIA had met with Kim, 45, on several occasions, according to a Wall Street Journal report.

Details of the exact relationship between Kim and the CIA remain unclear but are said to be about to be revealed in a new book about Kim Jong Un, 35, titled “The Great Successor” by Anna Fifield.

Kim was assassinated in a Malaysian airport in 2017 when women smeared his face with what appeared to be a nerve gas. After reporting the incident to airport officials, he was rushed to the hospital but died in the ambulance.

He traveled to Malaysia in February 2017 to meet with his CIA contact, though it remains uncertain as to whether or not that was the sole purpose of the trip.

Kim lived primarily outside North Korea, usually residing just outside of China in Macau. Reports also say he was providing intelligence to several other countries. China was named specifically as a beneficiary of information.

Both the CIA and Chinese officials declined comment about the report.