US and South Korean agents are plotting to kill North Korean leader Kim Jong-un, state media report.
A statement by the ministry of state security said a terrorist group backed by the CIA and South Korea's intelligence agency had entered the country to attack with a bio-chemical substance.
It said North Korea would find and "mercilessly destroy" the terrorists.
It comes amid high tensions in the region.
The statement, carried by North Korean news agency KCNA, said the alleged plot included the use of "biochemical substances including radioactive substance and nano poisonous substance". The results would be visible after six to 12 months, it said.
A recent war of words between the West and Pyongyang has escalated in recent weeks, with North Korea threatening to carry out a sixth nuclear test.
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Credit: Bbc