Malaysian authorities were decontaminating Kuala Lumpur airport yesterday after it emerged that alleged North Korean agents used VX, one of the world's deadliest nerve agents, to assassinate the elder half-brother of Kim Jong-un.

Kim Jong-nam was murdered last week by a hit squad who smeared his face with VX, which is among the world's most dangerous chemicals, police said.

The announcement sent a tremor of alarm through the country and raised questions about how Malaysia's government had allowed passengers to travel through the terminal for more than a week without carrying out a decontamination.

Asked whether people should avoid the airport out of fears of contamination, Malaysia's police inspector-general Khalid Abu Bakar said: "No. No. No. But I don't know. I am not the expert."

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Abu Bakar said specialists were beginning to decontaminate the terminal where Kim was killed as well as other sites the suspected killers had visited. It is not known whether the VX could linger in the terminal or have delayed long-term effects on people who may have been exposed to it.

The nerve agent is considered a weapon of mass destruction and much of the world has committed to destroying its stockpiles of the deadly agent. However, North Korea retains one of the world's largest chemical arsenals and has ample supplies of VX. It is not clear if the alleged North Korean agents were able to smuggle the deadly weapon into Malaysia or if they assembled it inside the country. Both possibilities are alarming for the Malaysian security services.

The two women accused of killing Kim both appear to be in good health despite their contact with VX, although one of them began to vomit after her arrest, according to police.

Dr Bruce Goldberger, a toxicologist at the University of Florida, said it was possible that the two women had been given an antidote ahead of carrying out the killing, which would have spared them the worst effects of the toxin.

VX was developed in Britain in the 1950s by scientists doing research on pesticides. Iraq's dictator Saddam Hussein is believed to have used it against Kurdish opponents in the late 1980s and a Japanese death cult was able to kill one person in the mid-1990s by attacking them with VX.

The same cult, Aum Shinrikyo, used sarin gas - a cousin of VX - in an attack on the Tokyo subway system in 1995, which killed 12 people and badly injured dozens.

North Korea has denied responsibility for the murder, saying that the allegations were fabrications made on behalf of South Korea.

Malaysia has not formally accused the North Korean state of the assassination, but it has said that four North Korean men provided the two women with the deadly nerve agent. All four fled Malaysia shortly after Kim's death, police said.

Yesterday pictures emerged of the Vietnamese woman suspected of helping to kill Kim, posing on a motorbike in a bikini. Doan Thi Huong worked at an entertainment outlet, according to Malaysian police, who arrested her along with an Indonesian woman over the murder.

Huong is a keen singer and it is understood she was working at a motor show in Hanoi, Vietnam.

The last post on a Facebook page in the name of "Ruby Ruby", which family members confirmed to be one of Huong's accounts, is dated February 11 from Kampong Besut, Malaysia.

Security remains tight at Kuala Lumpur Hospital where the body of Kim Jong-nam was taken after his murder. Photo / AP
Security remains tight at Kuala Lumpur Hospital where the body of Kim Jong-nam was taken after his murder. Photo / AP