North Korea threatened Friday to launch an anti-terrorist attack against the intelligence agencies of South Korea and the United States as it accused them of plotting to kill North Korean leader Kim Jong-un.

North Korea's Ministry of State Security claimed that a terrorists' group supported by the CIA and South Korea's intelligence agency infiltrated North Korea to stage a terrorist attack against the North Korean leader by using a bio-chemical substance.

"We will ferret out and mercilessly destroy to the last one the terrorists of the U.S. CIA" and South Korea's National Intelligence Service, North Korea's Ministry of State Security said in an English-language statement carried by the North's official Korean Central News Agency.

"Korean-style anti-terrorist attack will be commenced from this moment to sweep away the intelligence and plot-breeding organizations of the U.S. imperialists and the puppet clique."

The ministry also warned that a series of more powerful "our-style anti-terrorism striking actions will begin immediately," though it did not give any further details.

The North's ministry claimed that South Korean intelligence agents conspired with the CIA and bribed a North Korean timber worker surnamed Kim in Russia in June 2014 and turned him into a terrorist.

It also claimed that South Korean intelligence agents handed Kim over US$20,000 on two occasions and a satellite transmitter-receiver after plotting to kill the North Korean leader through a bomb or biochemical substances.

North Korea's allegations could not be independently confirmed. Repeated calls to South Korea's National Intelligence Service seeking comment went unanswered.

The North's Ministry of State Security said terrorism is a common enemy to humankind, but the communist country is blamed for a terrorist attack that killed the estranged half brother of North Korean leader Kim Jong-un.

Kim Jong-nam was killed at Kuala Lumpur International Airport on Feb. 13 after two Asian women rubbed what the Malay police later said was nerve agent VX on Kim's face.

Eight North Koreans were named suspects in the case, though North Korea has denied any involvement and claimed that Malaysia colluded with South Korea on its probe into the case. (Yonhap)