The poison, which is classed as a weapon of mass destruction by the United Nations, was detected on swabs taken from his eye and face.
Mr Kim, who is the estranged half-brother of North Korean leader Kim Jong-Un, was attacked by two women at an airport in Kuala Lumpur on 13 February.
The suspects appeared to put a substance on his face while he checked in for a flight – and although Mr Kim sought help from airport staff shortly afterwards, he died on the way to hospital.
VX nerve agent is tasteless and odourless, and it is outlawed under the Chemical Weapons Convention except for “research, medical or pharmaceutical purposes”.
It can be made as a liquid, cream or an aerosol – and if it is consumed in large doses, it can kill someone within 15 minutes.
Investigators have previously said the two female suspects were trained to wash their hands immediately after the attack.
Toxicologists have been left stumped as to how the attackers managed to apply a poison and kill Mr Kim so quickly without becoming ill themselves.
But it has now emerged that one of the women also suffered effects, and was vomiting after the attack.
Malaysia’s police chief wants to question a North Korean embassy official about Mr Kim’s death – but have faced a stumbling block because he enjoys diplomatic immunity.
Inspector-General Khalid Abu Bakar said: “If you have nothing to hide, you don’t have to be afraid. You should co-operate.”
On Thursday, Pyongyang said Malaysia was to blame for Mr Kim’s death – and said the country’s government had shown an “unfriendly attitude” by refusing to hand over his body.
Vietnamese suspect Doan Thi Huang
Malaysian suspect Muhammad Farid bin Jallaludin
Indonesian suspect Siti Aisyah
North Korean suspect Ri Jong Chol
North Korean suspect Ri Ji Hyon
North Korean suspect Hong Song Hac
North Korean suspect O Joong Gil
North Korean suspect Ri Jae Nam
North Korean suspect Ri Ji U
Hyon Kwang Song is a diplomat at the North Korean embassy
Kim Uk Il is said to work for North Korean airline Air Koryo
According to KCNA, the country’s state news agency, Mr Kim “suddenly fell into a state of shock” and died after suffering what it called “a heart stroke”.
North Korean officials have challenged claims that the 45-year-old was poisoned, and maintain that Malaysian police have “recklessly” made this an established fact.
According to the secretive state’s KCNA news agency, the Korean Jurists Committee has expressed outrage at Malaysia’s decision to perform two post-mortem examinations on Mr Kim – describing it as “a wanton human rights abuse and an act contrary to human ethics and morality”.
North Korea has proposed a joint investigation with Malaysia and says it stands ready to send a delegation of jurists to “conclude the investigation into the incident in a fair way”.
The country says it wants to meet suspects, hear their statements, asked who ordered them, and survey footage from the place where Mr Kim fell ill.