NORTH Korea has accused the US and South Korean spy agencies of an unsuccessful assassination attempt on leader Kim Jong Un involving bio-chemical weapons.

In a statement carried on state media, North Korea’s Ministry of State Security said it would “ferret out and mercilessly destroy” the “terrorists” in the CIA and South Korean intelligence agency for targeting its supreme leadership.

North Korea frequently lambasts the United States and South Korea, but the latest accusation is unusual in its detail.

The ministry claimed that in June 2014 the spy agencies “ideologically corrupted and bribed” a North Korean citizen who had been working in Russia to carry out the alleged assassination on Kim after returning home.

It said South Korean agents gave money and satellite communication equipment to the North Korean to attack Kim during a public event with a bio-chemical weapon, such as a delayed-action radioactive or “nano-poisonous” substance.

The ministry said that after a series of contacts and payments, the agents told the North Korean last month that the type of bio-chemical substance had been decided and would be supplied by the CIA.

The statement added that in response to the alleged plot, a “Korean-style anti-terrorist attack will be commenced from this moment to sweep away the intelligence and plot-breeding organisations of the US imperialists and the puppet clique,” referring to South Korea.

The North Korean statement comes during a period of tension on the Korean peninsula over concerns that the North is preparing another nuclear test or missile launch, including a possible test of an intercontinental ballistic missile.

Such moves would be a step towards the country’s goal of developing nuclear-armed missiles capable of reaching the US mainland.

Earlier this year, North Korea was accused of using the chemical war agent VX to assassinate Kim’s exiled half-brother at Kuala Lumpur’s airport, which led to calls in the United States to relist the North as a state sponsor of terrorism.