The uncle of North Korean dictator Kim Jong Un has been executed as a traitor Thursday.

Jang Song Thaek, who had been considered the second most powerful official in the country, was killed immediately after a military trial. He was stripped of all posts and expelled from the Workers party for offences including factionalism, corruption and dissolute behavior.

The state-controlled Korean Central News Agency released a 2,700-word statement in English Friday.

'From long ago, Jang had a dirty political ambition,' the statement said. 'He dared not raise his head when Kim Il Sung and Kim Jong Il were alive.'

'He began revealing his true colors, thinking that it was just the time for him to realize his wild ambition in the period of historic turn when the generation of the revolution was replaced.'

The statement added: 'Every sentence of the decision served as sledge-hammer blow brought down by our angry service personnel and people on the head of Jang, an anti-party, counter-revolutionary factional element and despicable political careerist and trickster.'

'The accused is a traitor to the nation for all ages who perpetrated anti-party, counter-revolutionary factional acts in a bid to overthrow the leadership of our party and state and the socialist system.'

'The accused Jang brought together undesirable forces and formed a faction as the boss of a modern day factional group for a long time and thus committed such hideous crimes as attempting to overthrow the state.' KCNA added.

Jang, 67, had been seen as helping Kim Jong Un consolidate power after the death of his father, Kim Jong Il, two years ago. Jang was called a traitor for trying to seize absolute power, a stunning end for the supreme leader's former mentor.

Analysts say Kim Jong Un has acted swiftly and ruthlessly to bolster his own power and show strength.

But there are fears in South Korea that the removal of Jang and his followers could lead to instability, a political miscalculation

In the US, Patrick Ventrell, a spokesman for the National Security Council, said: "If confirmed, this is another example of the extreme brutality of the regime."