VX nerve agent killed Kim Jong-nam

North Korean leader Kim Jong-Un's half brother was assassinated with a lethal nerve agent manufactured for chemical warfare and listed by the UN as a weapon of mass destruction, Malaysian police said on Friday.

Malaysia's police chief Khalid Abu Bakar said the presence of the nerve agent had been detected in swabs taken from Kim Jong-nam's eyes and face.

One of the women Kim interacted with at the airport on February 13 had also fallen ill with vomiting afterwards, he added.

The authorities say they intend to decontaminate the airport and areas the suspects are known to have visited.

Khalid said other exhibits were still under analysis and that police were investigating how the banned substance might have entered Malaysia.

"We will get the experts from the atomic energy department to go to the location and sweep it to see if radioactive (material) is still there," the police chief told reporters.

"If the amount of the chemical brought in was small, it would be difficult for us to detect," he said.

Kim had been living in exile since 2003 after falling out of favour with his father, who had been lining up to succeed him as Supreme Leader.

Two women -- one Vietnamese and the other Indonesian -- are in custody along with a North Korean man. Investigators are also seeking seven other North Koreans wanted in connection with the case, including a diplomat pleading immunity at the embassy in Kuala Lumpur.

Airport CCTV footage shows the moment of the assault, with Kim later seen asking airport officials for medical help, and rubbing his eyes and stumbling as he entered a clinic.

Authorities said he complained of dizziness and died on the way to hospital.

VX is part of a family of nerve agents created decades ago during research into pesticides. It is tasteless and odorless and kills by causing uncontrollable muscle contractions, which eventually stop the victim from breathing.

VX nerve agent can be delivered in two compounds that are mixed at the last moment to create a lethal dose. A dose of about 10 milligrams is enough to kill by skin contact, according to the Federation of American Scientists.

The Chemical Weapons Convention bans the use and stockpiling of chemical weapons, and North Korea is among the world's largest possessors of such weapons. In 2014, the South Korean Defense Ministry said the North had stockpiled 2,500 to 5,000 tons of chemical weapons and had a capacity to produce a variety of biological weapons.

North Korea has accused Malaysia of being unduly influenced by South Korea's early claim that Kim was poisoned by the North.

Pyongyang's ambassador to Malaysia, Kang Chol, accused his host country of conspiring with "hostile forces," prompting the Malaysian Prime Minister to recall his ambassador to North Korea and summon Kang.

An article published in North Korean state media Thursday fiercely rebuked Malaysia for its continued refusal to hand over Kim's body without DNA from a next of kin.

"This proves that the Malaysian side is going to politicize the transfer of the body in utter disregard of international law and morality and thus attain a sinister purpose," Thursday's article said.