North Korea has accused the US and South Korean spy agencies of an unsuccessful assassination attempt against leader Kim Jong-un involving biochemical weapons.
In a statement carried on state media, North Korea's ministry of state security on Friday said that a "hideous" group sanctioned by the CIA and South Korean Intelligence Service (IS) had infiltrated North Korea "on the basis of covert and meticulous preparations to commit state-sponsored terrorism against the supreme leadership".
The ministry said the spy agencies in June 2014 "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 Jong-un during a public event with a biochemical weapon such as a delayed-action radioactive or "nano poisonous" substance.
The ministry said after a series of contacts and payments, the agents told the North Korean last month that the type of biochemical substance had been decided and would be supplied by the CIA.
It did not describe how the alleged plot was broken up or release the full name of the North Korean suspect, identifying him only by his surname, Kim, and did not say whether anyone else was in custody.
The statement said 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 US Embassy in Seoul and South Korea's National Intelligence Service were not immediately available for comment.
Earlier this year, Seoul accused Pyongyang of using the chemical war agent VX to assassinate Kim Jong-un's exiled half brother at Kuala Lumpur's airport, which led to calls in the US to relist the North as a state sponsor of terrorism. North Korea denied involvement.
Tensions have surged in the region in recent weeks in the wake of a series of North Korean missile tests and rhetoric from US President Donald Trump's administration on the country's weapons programme.
The US also deployed a naval strike group to the Korean Peninsula, angering Pyongyang, and US officials have said all options are on the table.