Kim Jong nam, the half-brother of North Korean leader Kim Jong un who was killed in Malaysia in 2017, was an informant for the Central Intelligence Agency in the United States, The Wall Street Journal reported on Monday.

The daily cited an unidentified “person knowledgeable about the matter” for the report. It said many details of Kim Jong nam’s relationship with the US spy agency remained unclear. “There was a nexus” between the CIA and Kim Jong nam, The Wall Street Journal quoted the person as saying. The CIA declined to comment on the claim.

“Several former US officials said the half brother, who had lived outside of North Korea for many years and had no known power base in Pyongyang, was unlikely to be able to provide details of the secretive country’s inner workings,” the report said.

The former officials also said Kim Jong nam had almost certainly been in contact with security agencies of other countries, particularly China’s.

The newspaper’s source said Kim Jong-nam travelled to Malaysia in February 2017 to meet his CIA contact, although that may not have been the sole purpose of the trip. Kim Jong nam was assassinated at the Kuala Lumpur airport. Two women were arrested for killing him. Four men, suspected to be North Korean agents, were suspected to have orchestrated the assassination.

South Korean and US officials have said North Korean authorities ordered the assassination of Kim Jong-nam, who was critical of his family’s dynastic rule, an allegation Pyongyang has denied, according to The Guardian.