“We are shocked by the latest revelation by the Malaysian authorities that VX… was used in the death of Kim Jong Nam,” Seoul’s foreign ministry said in a statement today.

It called it a “blatant violation of the Chemical Weapons Convention and other international norms”.

Unlike Pyongyang, Seoul – which first pointed the finger at North Korea over Jong Nam’s death – is a signatory to the Convention, which went into force in 1997.

“The use of any chemical weapons is strictly banned for any reason and in any place,” the foreign ministry statement said.

South Korea’s defence ministry said in its 2014 Defence White Paper that North Korea began producing chemical weapons in the 1980s and estimated that it has about 2,500 to 5,000 tonnes in stock.

In a 2015 assessment, the Washington-based Nuclear Threat Initiative wrote: “North Korea claims that it does not possess chemical weapons.

“While assessing stockpiles and capabilities are difficult, the DPRK (Democratic People’s Republic of Korea) is thought to be among the world’s largest possessors of chemical weapons, ranking third after the United States and Russia.”