The half brother of North Korea's Kim Jong Un - who was assassinated in Kuala Lumpur International Airport in Malaysia in February 2017, when two women smeared his face with the nerve agent VX - was an informant for the Central Intelligence Agency and met with agency operatives on several occasions, Wall Street Journal reports, citing a person who knew about the matter.

Kim Jong Nam was once considered to be the heir to late North Korean leader Kim Jong Il but he fell out of favor with his father in 2001 after he was caught trying to enter Japan on a false passport, and was arrested at Tokyo airport, apparently en route to Disneyland. Kim Jong Nam had been critical of Kim Jong Un, reportedly saying in 2012 that he “won’t last long” because of his youth and inexperience. The two brothers have different mothers, Bloomberg reports.

While details of Kim’s relationship with the CIA are not clear, several former U.S. officials told WSJ that he had no known power base in Pyongyang and would unlikely be able to give details of North Korea’s inner workings. The same unnamed U.S. officials also told the Journal that Kim was also in contact with security services of China.

WSJ notes that the CIA has long taken an intensive interest in North Korea, although its totalitarian culture, and the lack of a U.S. embassy there, makes it one of the agency’s hardest targets. As Joel Wit, a former State Department official and senior fellow at the Stimson Center think tank, noted:

“My experience has been that the CIA has repeatedly thought that it had well-placed sources in North Korea, human sources, that really knew what was going on... Those sources have more often than not proved to not know what’s going on.”

The two women involved in Kim Jong Nam's murder have since been released from Malaysian prison.