By James Griffiths CNN

(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, North Korean state news agency KCNA said a "hideous terrorist group" conspired with the CIA and South Korea's Intelligence Service (IS) to "commit bomb terrorism targeting the supreme leadership" during major events including a recent military parade.

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.

IS did not respond to a request for comment.

CIA accused

The KCNA report claimed the plot was "recently uncovered and smashed," and accused members of the CIA and IS of working with a North Korean citizen to provide money and weapons to carry out "state-sponsored terrorism."

A similar charge was laid against Pyongyang by Seoul in February following the murder of Kim Jong Nam, allegedly at the hands of North Korean agents.

The half-brother of Kim Jong Un was poisoned with the VX nerve agent while in Kuala Lumpur airport and died en route to a hospital.

North Korea has repeatedly denied any involvement in Kim's death.

History of unfounded claims

North Korea has a history of bombastic propaganda featuring unfounded claims.

Last month, the state-run newspaper Rodong Sinmun claimed US-Australian military exercises in northern Australia were preparation for nuclear war against North Korea and threatened Darwin with a potential retaliatory strike.

For its part, South Korea has admitted to having plans in place to kill Kim.

Last year, lawmakers said Seoul "has a general idea and plan to use precision missile capabilities to target the enemy's facilities in major areas as well as eliminating the enemy's leadership."

The country's Joint Chiefs of Staff has prepared a system called the Korea Massive Punishment and Retaliation (KMPR) that would involve surgical missile attacks, exclusive special warfare units and an ability to strike North Korea's leadership if South Korea feels threatened by nuclear attack.

TM & © 2017 Cable News Network, Inc., a Time Warner Company. All rights reserved.