Only days after allegedly having his former mistress and 12 others executed by machine gun, North Korean dictator Kim Jong-un has sacked the head of the country's army in what observers believe may the beginning of a purge at the top of the secretive state's armed forces.

Analysts claim that Kim, who is believed to be 30, may be attempting to consolidate power by replacing veterans who served under his father with younger men more amenable to his vision.

Kim Kyok-sik, 75, whose stern features were a familiar sight in pictures alongside Kim's father, Kim Jong-il, at public appearances, is believed to have masterminded the torpedoing of the South Korean Navy ship, Cheonan, and the shelling of the south's Yeonpyeong Island, both in 2010.

He is thought to have been replaced by former staff chief Ri Yong-gil.

Seoul-based North Korean analyst Daniel Pinkston, said: "He is replacing officers appointed by his father, Kim Jong-il, with younger men who he hopes will now shore up his political power base.

"He hopes that by appointing these men it will make them beholden to him. And he has had to make these changes piecemeal because if he had started sacking large numbers of his generals at the same time, that could have led to a rebellion."

A source in the South Korean government said: "We're closely watching developments in the North, believing that Kim Kyok-sik has been replaced by Ri Yong-gil, the Army's General Staff chief of operations."

He said the information was gleaned from a close study of North Korean media, and that a North Korean paper had mentioned Ri Yong-gil behind senior regime figures Choe Ryong-hae and Jang Song-taek in a report about Kim watching a football match alongside selected soldiers.

It mentioned Ri before Jang Jong-nam, the minister of the People's Armed Forces, but significantly there was no mention at all of Kim Kyok-sik, who was always previously photographed at Kim's side.

In addition, Ri's uniform was decorated with four stars, rather than the three stars he was photographed with last year.

"Ri seems to have been promoted to chief of the Army's General Staff, because the chief of operations is never mentioned ahead of the Armed Forces minister," said the source, quoted in Seoul's authoritative Chosn Ilbo newspaper.

The report claims that Kim Kyok-sik's dismissal may have been discussed at a meeting of the Workers Party's Central Military Commission, which Kim chaired.

In North Korean media it was reported that the leader had discussed "organisational matters" and had made an "important decision" at the meeting.