KUALA LUMPUR (THE STAR/ASIA NEWS NETWORK, REUTERS) - Kim Jong Nam would have died a "horribly painful" death after being poisoned by the VX nerve agent, which is one of the deadliest chemical weapons created by man, experts said on Friday (Feb 24).

Just 10mg of the nerve agent or a single drop is enough to kill in minutes, experts say. The toxin jams the nervous system and causes the victim to die of suffocation.

Dr Dzulkefly Ahmad, a former Universiti Sains Malaysia toxicologist, told The Star Online: "It is a very frightening agent. It was used in chemical warfare and I was a part of the team that studied it for the Iran-Iraq war in the 1980s.

"In this case, from what I see, it was dermal inhalation, which means it must be acute toxicity.

"These neurotoxic agents act on enzymes of the neurochemical system, which then attempt to shut down your system. This is when the victim goes through suffocation and will eventually collapse," he said.

Malaysian police said earlier on Friday that VX was found on the body of Jong Nam, the estranged half-brother of North Korean leader Kim Jong UN, at the Kuala Lumpur International Airport on Feb 13. Police were investigating how the chemical entered the country.

Inspector-General of Police Tan Sri Khalid Abu Bakar also said that one of the two women who allegedly carried out the attack was unwell as a result of poisoning from the same chemical.

Dr Dzulkefly said there is no antidote for high dosages of the VX agent.

On the attack suspects - Vietnamese Doan Thi Huong, 28, and Indonesian Siti Aisyah, 25 - the former professor said they could not have touched the chemical with their bare hands or even normal gloves as VX can be absorbed through the skin and causes severe poisoning.

"The women who put the chemical on his face must have guarded themselves well and must have contained the liquid well until the point they had to put it on his face."

On one of the two women vomiting because of exposure to the chemical in a low dosage, Dr Dzulkefly said it was one of the effects of VX.

"It happens when they are not properly protected. You can have diarrhoea and vomiting. But such levels of exposure would not lead to death as there are antidotes for it.

"But when the dosage is massive (10mg or above), then it is lethal," he said.

HARD TO PRODUCE

With the texture and feel of engine oil, VX was first produced in Britain in the 1950s. It can cause convulsions, loss of consciousness, paralysis and respiratory failure in minutes.

Its only known use is as a chemical warfare agent: VX is classified as a weapon of mass destruction by the United Nations.

"You can think of VX as being a pesticide on steroids, this is an extraordinarily toxic substance. Roughly 1/100th of a gram, a third of a drop, on someone's skin, will kill them," said Mr Bruce Bennet, defence researcher at California-based RAND Corporation.

VX and other nerve agents were believed to have been used in chemical warfare during the Iran-Iraq War in the 1980s. In 2015, traces of VX and sarin - another nerve agent - were found at a military research site in Syria that had not been declared to the global chemical weapons watchdog.

Sarin gas was used in Syria, killing hundreds in deadly attacks in 2013, and by members of a Japanese doomsday cult in their deadly 1995 attack on a Tokyo subway.

But VX is known to be much more potent than sarin and other nerve agents because of its persistency. Sarin evaporates from the skin surface but VX does not.

The chemical is hard to produce but a few countries are known to make it and remain in possession of it. The United States and Russia still have some VX stockpile.

South Korean analysts have identified sarin and VX as the focus of a North Korean chemical weapons programme. Pyongyang has denied that.

Symptoms after contact with VX in vapour form will appear within a few seconds, and within a few minutes to up to 18 hours after exposure to the liquid form.

VX is considered to be much more toxic by entry through the skin and somewhat more toxic by inhalation. Any visible VX liquid contact on the skin, unless washed off immediately, is believed to be lethal, according to the US government's Centres for Disease Control and Prevention (CDC).

BARE HANDS

People may not even know they have been exposed to VX as it is tasteless and odourless. In fact, it is unlikely to have been detected by airport security or sensors if it had been brought in in small amounts.

Kim Jong Nam was murdered at the Kuala Lumpur airport on Feb 13 while he was waiting in the departure hall to take a flight to Macau, where he was known to be living with his family for years under Chinese protection.

He had spoken out publicly against his family's dynastic control of the isolated, nuclear-armed state. South Korean and US officials say North Korean leader Kim Jong Un likely ordered the assassination of his half-brother.

North Korea unsuccessfully tried to prevent an autopsy on the body, accusing Malaysia of working with South Korean and other "hostile forces".

Pyongyang has said Malaysia should be held responsible for killing one of its citizens, though it has not acknowledged the victim is Mr Kim Jong Un's half-brother.

Malaysian police say two women are believed to have attacked Mr Kim Jong Nam, using their bare hands to wipe his face with a liquid. The women were then instructed to wash their hands afterwards.

The two women and a North Korean have been detained in Kuala Lumpur. Police are searching for seven other North Koreans, four of whom are believed to have fled to Pyongyang.