(CNN) North Korea has accused the US and South Korea of attempting to assassinate leader Kim Jong Un with a "bio-chemical substance."

In an extraordinary 1,800-word report Friday, which offered no evidence other than account laced with fantastical language, North Korean state news agency KCNA said a "hideous terrorist group" conspired with the CIA and South Korea's National Intelligence Service (NIS) to mount the attack.

Its aim, the report said was to "commit bomb terrorism targeting the supreme leadership" during major events including a recent military parade

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The report claimed a North Korean citizen was involved in the plot, using "biochemical substances including radioactive substance and nano poisonous substance" to target Kim.

North Korea has a history of making unfounded and irrational claims, and CNN was not able to independently corroborate the report. South Korea's intelligence service told CNN they know nothing about the alleged plot.

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