The Central Public Prosecutors Office said that it will "sternly punish the mastermind of state-sponsored terrorism and accomplices," releasing a list of four suspects, including Lee Byong-ho, South Korea's spy chief.

Lee is currently leading the National Intelligence Service, and will be replaced by Suh Hoon if Suh's appointment is approved by parliament.

The prosecutors announced the start of their indictment under the country's penal code, calling for a prompt extradition of them by Seoul and Washington.

"The US and South Korea shall promptly arrest all the organizers, participants and followers of the extra-large state-sponsored terrorist crime against the supreme leadership of (North Korea) and deliver them to it," the office said in an English statement carried by the Korean Central News Agency.

North Korea's claim could not be independently verified. South Korea's spy agency has dismissed it.

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

Pyongyang threatened to launch an anti-terrorist attack against Seoul and Washington's intelligence agencies, without unveiling details. (Yonhap)