Kim Jong-nam, the estranged half-brother of North Korean leader Kim Jong-un, died after being attacked with the banned VX nerve agent at Kuala Lumpur airport on February 13, Malaysian authorities said. He was waiting for a flight to Macau, where he lived with his family, when two women allegedly wiped chemicals on his face. He sought help from airport staff, suffered convulsions and died on the way to hospital. He was travelling on a passport bearing the name Kim Chol.

Malaysia’s police chief, Khalid Abu Bakar, said preliminary toxicology tests found VX on swabs from Kim’s eyes and face. Police were investigating how the substance entered Malaysia and said the two women, one Vietnamese and one Indonesian, had suffered vomiting after the attack. Relatives and acquaintances of the women insisted they must have been duped. Authorities detained several people and sought other North Koreans, including a diplomat and an airline employee.

VX is a highly toxic, oily nerve agent that can be absorbed through the skin, eyes, lungs or digestive system. A small amount can be fatal, and the substance can persist on surfaces. Its identification raised questions about public safety because the airport had gone days without decontamination. Malaysian authorities said no passengers, airport workers or medical staff who treated Kim had reported illness; they planned to decontaminate areas visited by the suspects.

The killing triggered a diplomatic dispute between Malaysia and North Korea. Malaysian investigators alleged that North Korean agents organised the attack. Pyongyang denied involvement, criticised the investigation and blamed Malaysia for the death of its citizen. It did not acknowledge that the dead man was Kim Jong-nam, and Malaysia sought to question a senior member of the North Korean embassy.

Kim Jong-nam was once considered a potential successor to his father, Kim Jong-il, but lived abroad after being passed over in favour of Kim Jong-un. He later criticised the regime’s policies and dynastic succession.

VX is banned under the Chemical Weapons Convention, which North Korea has not signed. Estimates cited in the reports put North Korea’s chemical weapons stockpile at 2,500 to 5,000 tonnes and its annual production capacity as high as 4,500 tonnes in a typical year. The passages also recalled an earlier use of homemade VX by Japan’s Aum Shinrikyo cult in 1994 and 1995, when three people were attacked and one died.