South Korean agencies say they cannot confirm a report that the half brother of North Korean leader Kim Jong Un was a U.S. intelligence source and traveled to Malaysia to meet his CIA contact before being assassinated there in 2017.

Officials at South Korea's National Intelligence Service and Unification Ministry said Tuesday they couldn't confirm Monday's report by The Wall Street Journal, which attributed the details to an unidentified "person knowledgeable about the matter."

It's extremely difficult to verify information about North Korea's ruling family.

Kim Jong Nam was killed by VX nerve agent. Murder charges were dropped against the two women who smeared it on his face.

The Journal said Kim Jong Nam met several times with CIA operatives but details of his relationship with the agency remain unclear.