Story highlights North Korean defector says Kim Jong Un's cruelty is shocking

Park claims Kim ordered his some of his closest aides to be killed -- as well as their families

Interview is Park's first since defecting from North Korea

Seoul, South Korea (CNN) While the late Kim Jong Il imprisoned his enemies, his son and current North Korean leader simply executes them, says one of the highest-level officials to escape the isolated country in years.

A man we are referring to simply as Park to protect his identity tells CNN, in his first-ever interview, that Kim Jong Un's cruelty is shocking those around him.

He says, while his father and grandfather Kim Il Sung were both considered cruel by many around the world, Kim Jong Un is taking ruling by fear to a new level.

"During his first three years in power, hundreds of the elite have been executed," Park says, adding this brutality is shaking an already weak support base.

Much of what Park tells us cannot be independently confirmed, as North Korea is one of the most closed and repressive countries on Earth.

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