Kim Jong-nam, the estranged half-brother of North Korean leader Kim Jong-un, died after being attacked with the banned nerve agent VX at Kuala Lumpur International Airport, Malaysian police said. Preliminary toxicology tests detected the substance on his face and eyes following the February 13 attack.

Security footage showed a woman approaching Kim and wiping something across his face as he waited for a flight to Macau, where he lived with his family. He sought medical help, suffered convulsions and died on the way to hospital. He was travelling on a passport bearing the name Kim Chol.

Malaysian investigators said two women, one Vietnamese and one Indonesian, applied the poison to Kim’s face and that North Korean agents were involved. One woman later suffered vomiting, police said. Relatives and acquaintances of the women maintained that they had been deceived, while Malaysian authorities said their actions indicated awareness that they were handling a toxin. Police detained suspects and sought several North Koreans for questioning, including an embassy official and an employee of North Korea’s state airline.

VX is a highly toxic, persistent nerve agent that can be absorbed through the skin. Even a tiny amount can be fatal. It is banned under the Chemical Weapons Convention, which North Korea has not signed. The finding raised questions about public safety at the airport, where authorities began decontamination roughly 11 days after the attack. Police said no one else who came into contact with Kim had reported becoming ill, apart from one of the women accused in the attack.

North Korea denied responsibility, challenged Malaysia’s investigation and accused its authorities of fabricating evidence under South Korean influence. It also objected to the post-mortem examination and blamed Malaysia for the death. North Korea had not acknowledged that the dead man was Kim Jong-nam. The dispute strained relations between the two countries, and Malaysia warned the North Korean ambassador over his statements.

Kim Jong-nam was the eldest son of former North Korean leader Kim Jong-il and had once been considered a possible successor. He later lived abroad and criticized the country’s policies and hereditary leadership. Outside estimates cited in the reports put North Korea’s chemical weapons stockpile at 2,500 to 5,000 tonnes, potentially including VX, though Pyongyang’s responsibility for the killing remained disputed.