North Korea said on Thursday there were strong indications that a heart attack may have killed the North Korean national who died at the Kuala Lumpur International airport.

Malaysia has said the man, identified as Kim Jong Nam, the estranged half-brother of the North Korean leader Kim Jong Un, was killed with the super toxic nerve agent VX. North Korea has denied the dead man in Kim Jong Nam.

A former North Korean deputy ambassador to the United Nations said Ri Tong Il said samples of the toxic substance found in the autopsy should be sent to the Organisation for the Prohibition of Chemical Weapons (OPCW).

"If it is true that it was used, then the samples should be sent to the office of OPCW," he told reporters, on the alleged use of VX.