MALAYSIAN officials trying to determine whether poison killed Kim Jong Nam, the half brother of North Korean leader Kim Jong Un, in a busy airport are baffled by post-mortem tests which have so far been inconclusive.

More than a week has passed since Kim Jong Nam was approached by two women at a budget airline terminal in Kuala Lumpur, where he was then apparently sprayed in the face with an unknown substance.

He did not suffer a heart attack and had no puncture wounds, such as those a needle would have left, according to Noor Hisham Abdullah, director general of health, who did not dismiss poison as a potential cause.

He added that medical specimens have been sent to experts for analysis.

The case has perplexed leading forensic toxicologists who study murder by poison. They say the airport attack is one of the most bizarre cases on record, and question how the two women could walk away unscathed after deploying an agent potent enough to kill Kim before he could make it to hospital. Some type of nerve gas or ricin, a deadly substance found in castor beans, have been suggested as possible toxins used.

A strong opioid compound could also have been liquidised, although would probably have incapacitated the victim immediately. Surveillance footage shows Kim walking calmly downstairs to the airport’s clinic.

The older half brother of North Korea’s reclusive ruler Kim Jong Un is believed to have had at least three children with two women, but no family members have come forward to claim the body.