Releasing a preliminary toxicology report on Kim Jong Nam's murder at a Kuala Lumpur airport, police said the poison used by the assassins was the odourless, tasteless and highly toxic nerve agent VX.
Traces of VX were detected on swabs of the dead man's face and eyes.
Authorities intended to decontaminate the airport, along with other locations that suspects, three of whom were caught last week, had visited.
Leaked CCTV footage from the brazen attack on February 13 shows the portly Kim being approached by two women who appear to put something in his face.
Moments later he is seen asking for help from airport staff, who direct him to a clinic.
Malaysian police said he suffered a seizure and died before he reached hospital.
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Malaysia seeking North Korean diplomat over Kim Jong-nam killing
The Sepang District Police office where reportedly people were remanded in connection with the death of Kim Jong-nam. Source: AAP
Malaysian detectives are holding three people -- women from Indonesia and Vietnam, and a North Korean man -- but want to speak to seven others.
North Korea’s state media broke a 10-day silence Thursday on the murder launching a ferocious assault on Malaysia for "immoral" handling of the case and for playing politics with the corpse.
The North's official KCNA news agency said Malaysia bore prime responsibility for the death, and accused it of conspiring with South Korea.
It also condemned the Malaysian authorities for not releasing the corpse "under the absurd pretext" that it needs a DNA sample from the dead man's family.
North Korea has never acknowledged the victim as the estranged brother of leader Kim Jong-Un and the lengthy KCNA dispatch avoided any reference to the dead man's identity, calling him only "a citizen" of North Korea "bearing a diplomatic passport".
The only known use of VX is as a chemical warfare agent and the US government's Centers for Disease Control and Prevention (CDC) describes it as the "most potent" of all nerve agents.
"It is possible that any visible VX liquid contact on the skin, unless washed off immediately, would be lethal," the CDC said on its website.
All nerve agents cause their toxic effects by preventing the proper operation of an enzyme that acts as the body's "off switch" for glands and muscles.
Without that switch, the glands and muscles are constantly being stimulated, and eventually tire and become unable to sustain breathing.
Malaysian police looking for source of chemical used to kill Kim Jong-Nam
Malaysian police are investigating whether the VX nerve agent used to kill Kim Jong-Nam, the estranged half brother of North Korea's leader, was brought into the country or produced in Malaysia, the country's police chief said on Friday.
"We are investigating it," police chief Khalid Abu Bakar told reporters on the sidelines of an event. "If the amount of the chemical brought in was small, it would be difficult for us to detect."
Kim Jong Nam was murdered at Kuala Lumpur International Airport on February 13.
