As the Korean peninsula teeters on the brink of war, North Korea's former top female spy has revealed details of the state's most deadly terrorist attack.

In a world exclusive interview with the ABC's 7.30, the now-exiled Kim Hyun-hee tells of life inside the kingdom and how she was groomed by North Korean spy masters to plant a bomb on a South Korean passenger plane.

The 1987 attack killed all 115 people on board and led to the United States listing North Korea as a state sponsor of terrorism.

"From the moment I got on the Korean Air flight, left the bomb in the overhead locker, and until I got off, I was nervous every second of the operation," she said.

Kim recalls years earlier when she was plucked from a North Korean schoolyard to start spy training.

"In North Korea, I was taught that our leader Kim Il-sung was a god. You were taught to put him before your own parents," she said.

"You learn from early childhood to say 'Thank you, Great Leader' for everything. And if you said the wrong thing, even if it was a slip of the tongue, you'd end up in the gulag.

"North Korea is a not a state, it's a cult."

In the 1970s the regime quickly noticed the teenager because of her sharp intelligence, beauty and her ability to speak Japanese.

"One day a black sedan showed up at my school. They were from the central party and told me I'd been chosen," she said.

"I wasn't even allowed time to say goodbye to my friends, I was just told to pack. I was given one last night with my family."

In 1980 Kim Hyun-hee was sent to North Korea's elite spy training school in the remote mountains, she was given a new name and intensive training in martial arts, weapons and languages.

Femme fatale: Kim Hyun-hee during her days as a secret agent. ( ABC: Supplied )

After nearly eight years of learning spycraft, Kim was ready for her defining mission, one devised by the son of the founder and the country's future dear leader, Kim Jong-il.

"In North Korea, you needed Kim Jong-il's approval for the most minor thing, not to mention a spy mission. He personally ordered the operation to bomb the Korean Air flight," she said.

The ultimate target of Kim's mission was the 1988 Seoul Olympics. Jong-il hoped the bombing of Korean Air Flight 858 would scare foreign teams into staying away from the Games.

To carry out the mission, Kim Hyun-hee was teamed up with legendary North Korean spy Kim Seung-il.

Together they flew from Pyongyang to Moscow and then travelled to Budapest where they were given fake Japanese passports and began posing as father and daughter touring Europe together.

"Me and my partner had experience as agents in Europe. We were confident there and knew how the airports worked," she said.

They then headed to Baghdad, where they prepared for the final stage of their mission.

There they boarded a South Korean airliner carrying a bomb hidden inside a transistor radio.

Kim Hyun-hee had set the timer on the bomb to explode nine hours after Flight 858 took off - as the plane was in the air en route to Seoul.

After stowing the bomb the two North Koreans left the plane during a stopover in Abu Dhabi and made their way to Bahrain.

Not long after, the plane went down carrying 115 passengers.

'Nowhere to run'

Mission over: Kim Hyun-hee after her arrest in 1987. ( AFP )

Back in Bahrain, 25-year-old Kim was desperately trying to make her escape.

"We had nowhere to run. We had to get out of Bahrain. But our next plane didn't leave for two days. I was so anxious, it was driving me crazy," she said

Two days later Kim and her partner were confronted by authorities who realised they had been travelling on fake passports.

As they were being searched, the veteran agent Kim Seung-il told his young comrade it was time to bite down on an ampoule of cyanide hidden in their cigarettes.

"He said 'what awaits us is interrogation, and eventually death. I have lived a long time and am an old man. But you are so young. I am sorry'," she said.

"I knew when an operation failed, an agent had to kill themselves. So I bit down on the cyanide ampoule. As I did I remembered my mother in North Korea. Then I blacked out."

The older agent died almost immediately, but Kim Hyun-hee was revived and after recovering she was flown to South Korea to stand trial.

At first, Kim says she refused to give in to her interrogators, but it was not until they took her driving through the streets of Seoul that she realised all the lies she had been fed by the North Korean regime.

"I saw how modern it was," she said.

"I listened to how the agents around me spoke so freely. This contradicted everything I'd been told in North Korea. I realised then I'd taken innocent lives and I expected to be given the death sentence."

Kim was sentenced to death but later pardoned, with the South Korean government deciding she was merely a brainwashed victim of the Kim cult.

She now lives at a secret location in South Korea, surrounded at all times by six bodyguards, fearful that North Korean assassins may strike at any time.

"I deserved the death penalty for what I did. But I believe my life was spared because I was the only witness to this terror perpetrated by North Korea," she said.

"As the only witness, it is my destiny to testify about the truth."

Horror of the North

North Koreans attend a rally in Pyongyang supporting Kim Jong-un last month. ( Reuters: KCNA )

To Kim Hyun-hee, the fact that a third generation of the Kim dynasty is threatening the world is horrifying.

She knows those suffering the most are the millions doomed to live, work and die under the heel of the regime, including the family she had to leave behind.

"I once heard a story that a defector saw my family in a concentration camp about 15 years ago," she said.

"But to this day I have no idea what happened to my family."

She believes the latest sabre-rattling from North Korea is all an effort for the untested leader, Kim Jong-un, to play the tough guy in front of his domestic audience.

"Kim Jong-un is too young and too inexperienced," she said.

"He's struggling to gain complete control over the military and to win their loyalty.

"That's why he's doing so many visits to military bases, to firm up support."

She says the effects of the regime and what it compelled her to do will haunt her for the rest of her life.

"I regret what I did and am repentant. I feel I should not hide the truth to the family members of those who died," she said.

"It is my duty to tell them what happened."