North Korea rejects that version of events, saying that the women would be dead if they had put a lethal chemical on their hands. It vehemently denies any involvement in Kim's death.

Binary systems are usually employed for the safe storage of chemical weapons.

How it works

VX inhibits the operation of an enzyme that helps the body's nervous system function, causing paralysis and suffocation.

"VX is probably the state-of-the-art nerve agent," CNN military analyst Rick Francona said. "It is probably the most lethal of all the nerve agents ever designed."

Symptoms can appear after a few seconds, and even small doses -- as little as 10 mg on the skin -- can affect people. Larger exposure can lead to convulsions, paralysis and deadly respiratory failure.

VX is most dangerous when inhaled, rather than absorbed through the skin, according to Nial Wheate, a chemical weapons health expert at the University of Sydney.

"It's not (meant as) a skin agent. It's a thing that you aerosol through the air," he said.

Despite its lethality, it's not particularly difficult to make, Francona and other experts say.

But the blast from a delivery system like missile would likely destroy much of the VX, said Wheate. It's more meant for aerosol use in close quarters.

"There's no one weaponizing this stuff, this is old school," he said.

The suspects

Malaysia authorities have named 11 people in connection with their investigation, though not all are considered suspects.

Three are currently in custody. One is a North Korean man, and two are the women who police believe wiped Kim's face: Siti Aishah of Indonesia and Doan Thi Huong of Vietnam.

"These two ladies were trained to swab the deceased's face," he said. "They knew it was toxic."

Denials and diplomatic fallout

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.

Bakar, the Malaysian police inspector-general, accused North Korea of impeding the investigation.

He said Wednesday that the North Koreans had neither responded to requests to hand over the four suspects in Pyongyang, nor had they helped police find three North Koreans believed to be in Malaysia -- including an embassy employee -- who are wanted for questioning.

If the three who police think are still in Malaysia do not come forward, they will seek arrest warrants, Bakar said.