US says North Korea used chemical warfare agent to assassinate Kim Jong Un's half-brother

North Korea used a chemical warfare agent to assassinate the half-brother of its leader Kim Jong Un in Malaysia last year, the US has concluded and imposed new sanctions against the reclusive nation to stop its unlawful activities.

The US' claim came just hours after North Korea signaled it was willing to give up its nuclear weapons. Kim Jong-nam, the estranged half-brother of North Korean leader Kim Jong-un, died after two women approached him and smeared a deadly nerve agent on his face in Malaysia on February 13 last year.

The US determined on February 22 under the Chemical and Biological Weapons Control and Warfare Elimination Act of 1991 (CBW Act) that the Government of North Korea used the chemical warfare agent VX to assassinate Kim Jong Nam, in the Kuala Lumpur airport, State Department Spokesperson Heather Nauert said.

VX is an extremely toxic synthetic chemical compound. VX fatalities occur with exposure to tens of milligram quantities via inhalation or absorption through skin. On such exposure, it severely disrupts the body's signalling between the nervous and muscular systems, leading to a prolonged neuromuscular blockade, flaccid paralysis of all the muscles in the body including the diaphragm, and death by asphyxiation.

The US imposed new sanctions on North Korea as part of its finding, the State Department said. These sanctions are in addition to existing US comprehensive sanctions against targeting unlawful North Korean activities.        

The new sanctions took effect upon the publication of US' finding about the murder of Kim Jong Nam  in the Federal Register on Monday, Nauert said. Under the US law, when a country or leader violates its ban on chemical and biological weapons, an import ban is imposed on its products. North Korea is already under severe US and UN sanctions and so yesterday's decision will have little impact on the country.

"The US strongly condemns the use of chemical weapons to conduct an assassination. This public display of contempt for universal norms against chemical weapons use further demonstrates the reckless nature of North Korea and underscores that we cannot afford to tolerate a North Korean WMD program of any kind," Nauert said.

The new findings came as US President Donald Trump said that he believed that North Korea's offer to hold denuclearisation talks was "sincere." North Korea has offered to freeze its nuclear and missile programmes if the US begins direct talks on an agreement that would eventually see a nuclear free Korean peninsula.

But relations between the US and North Korea remain fragile. The North Korean regime has denied it was involved in Kim Jong-nams death and the new findings could disrupt diplomatic efforts.