Kim Jong Nam, North Korean leader Kim Jong Un’s assassinated half-brother, was reportedly an informant to the US Central Intelligence Agency (CIA) and had met with US officials multiple times, according to people familiar with the matter who spoke to the Wall Street Journal.

According to one anonymous source, "there was a nexus" between the CIA and Kim Jong Nam. However, the details of Kim Jong Nam's relationship with the CIA are unknown. In addition, the source revealed that US intelligence officials were relieved that Kim Jong Nam's connection to the CIA was not revealed following his assassination.

However, three months after his death in May 2017, Japanese newspaper Asahi Shimbun revealed that Kim Jong Nam had met with a Korean-American believed to be a US intelligence official by Malaysian authorities in Malaysia.

Kim Jong Nam's alleged link to the CIA will also be discussed in the "The Great Successor," a book written by Washington Post reporter Anna Fifield, scheduled to be published June 11.

However, several US officials told the Wall Street Journal that the half brother was unlikely to have provided confidential information on the isolated country because he lived outside North Korea for "many years" in Macau, an autonomous city on the southern coast of China, and "had no known power base in Pyongyang," the Wall Street Journal reported.

Former US officials also said that Kim Jong Nam was "almost certainly in contact with security services of other countries, particularly China's." However, both Chinese officials and the CIA refused to corroborate this information to the outlet. Several US officials and analysts from other countries, such as China, believed that Kim Jong Nam was a potential successor to Kim Jong Un, according to sources. However, US intelligence agencies had come to the conclusion that Kim Jong Nam wasn't capable of taking over that role.

The North Korean leader's half brother was killed at the Kuala Lumpur International Airport in Malaysia in February 2017 when two women smeared the nerve agent VX on his face. A Vietnamese woman named Doan Thi Huong and an Indonesian woman named Siti Aisyah were both charged with Kim Jong Nam's murder.

In April, Doan pleaded guilty to "voluntarily causing hurt by dangerous weapons or means" and was released from prison in May. The court dropped the charges against Siti in March. Both women claimed that they believed they were a part of a prank for a reality TV show when they attacked Kim Jong Nam.

During the trial of the two women, police testified that during Kim Jong Nam's final trip to Malaysia, he had met with an unnamed Korean-American man at Langkawi, off the northwestern coast of the Malay peninsula.

Joel Wit, a former State Department official and senior fellow at the Stimson Center think tank, recently told the Wall Street journal that the CIA occasionally obtained information from North Korean defectors on the country's weapons program and missile exports.

"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," Wit said. "Those sources have more often than not proved to not know what's going on."

In May 2017, the CIA established a North Korea Mission Center "to more purposefully integrate and direct CIA efforts against the serious threats to the United States and its allies emanating from North Korea," then CIA Director Mike Pompeo said at the time. "It also reflects the dynamism and agility that CIA brings to evolving national security challenges."