North Korea on Friday accused the U.S. Central Intelligence Agency and South Korea's intelligence service of a plot to attack its "supreme leadership" with a bio-chemical weapon and said such a "pipe-dream" could never succeed.
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 U.S. imperialists and the puppet clique", referring to South Korea.
He said North Korea's aim could be to divert attention from the use of VX nerve gas to assassinate the estranged half-brother of Kim Jong Un at Malaysia's Kuala Lumpur International Airport in February, or to influence South Korea's May 9 election.
Analysts say such an assassination operation would be extremely hard to plan and carry out given the massive security around the supreme leader.
Pyongyang presented extensive details but offered no concrete proof.
"They told him that assassination by use of biochemical substances, including radioactive substance and nano poisonous substance, is the best method that does not require access to the target, their lethal results will appear after six or twelve months", the statement said. Kim - described as "human scum" - received payments totalling at least $740,000 and was given satellite transceivers and other materials and equipment, it said.
Checks on China's National Enterprise Credit Information system show that a company of that name was formed on March 7 this year, with a Xu Guanghai named as its legal representative, and business areas including "chemical products".
The plot was foiled, it said, but gave no details on the fate of "Kim".
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 Central Intelligence Agency.
The lurid accusations come with Pyongyang and Washington at loggerheads over the North's banned weapons programs, which have seen it subjected to multiple sets of United Nations Security Council sanctions.
In 2012, North Korea's military warned that its troops had aimed artillery at the specific coordinates of South Korean media groups over their critical reports on children's festivals that had been taking place in Pyongyang, threatening a "merciless sacred war" over perceived insults.
The ministry termed the assassination plot as "the most vicious challenge and the declaration of a war" against the North and warned that it will not tolerate such "evil" plots hatched by the "dishonest hostile forces".