North Korea's former top female spy has spoken out from hiding about the regime's latest war mongering and why she thinks it is all about shoring up support for young leader Kim Jong-un.

In a world exclusive interview on tonight's 7.30, Kim Hyun-hee relives her life as an agent for the hermit kingdom, offering a rare insight into the regime.

In 1987, Kim planted a bomb on a South Korean plane that left 115 people dead.

She was later caught and after trying to kill herself with poison, she was given the death sentence by a South Korean court.

She was pardoned a few years later and now lives in the South at an undisclosed location, surrounded by bodyguards and still fearful that North Korean assassins could strike at any time.

In her exclusive interview, Kim tells the ABC she thinks the latest rhetoric out of Pyongyang is all about cementing the position of Kim Jong-un.

"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."

The former spy says there is method in the North Koreans' madness in threatening thermo-nuclear war.

"North Korea is using its nuclear program to keep its people in line and to push South Korea and the United States for concessions," she said.

Kim also reveals she believes she deserved the death penalty and is repentant about her actions.

She says she does not want to hide the truth from the families of her victims and feels it is her duty to tell them what happened.