Park in 1972 changed the constitution to perpetuate his rule. He was assassinated in 1979.
Regarding the bombing of a Korean Airlines plane over the Andaman Sea off Burma in 1987, which killed all 115 aboard, the NIS confirmed the plane was blown up by a time-bomb planted by North Korean agents.
Two North Korean agents were captured afterwards in Bahrain but the man committed suicide while his female companion was taken to Seoul.
She later made a chilling confession that they blew up the plane on orders from Pyongyang to try to scare away foreigners from the 1988 Seoul summer Olympics.
The NIS said its immediate predecessor, the National Security Planning Agency, had given rise to unwarranted conspiracy theories by conducting an over-hasty investigation and relying only on the testimony of the arrested agent, Kim Hyun-hee.
The agent was jailed but later pardoned and now lives in South Korea.
RSS