By Julian Ryall, Tokyo and Chris Irvine

Despite reports of him purging army generals and executing former girlfriends by firing squad, a survey carried out by the Institute for Peace and Unification Studies at Seoul National University on 133 North Korean defectors found that 61.7 per cent believed he had the majority support of his people.

Although not strictly scientifically accurate, as it polls defectors rather than people currently living there, such a result makes him more popular than his father, Kim Jong-il, while it also compares favourably to Barack Obama, who is struggling at 41 per cent approval, and David Cameron, who scored 38 per cent.

Mr Kim is meanwhile said to be keeping up his purge of undesirable elements within the upper echelons of North Korean society with the reported sacking of his hawkish army chief.

Kim Kyok-sik, who is believed to have been behind the sinking of the South Korean corvette Cheonan and the bombardment of Yeonpyeong Island in late 2010, has disappeared from the list of senior regime officials attending public events in recent weeks.

“We are closely watching developments in the North, believing that Kim Kyok-sik has been replaced by Ri Yong-gil, the chief of operations for the Army General Staff,” a source in the South Korean government told the Chosun Ilbo newspaper.

North Korean media have also pictured Ri with new four-star insignia.

Analysts believe that Kim Kyok-sik has been replaced as Kim Jong-un attempts to stamp his own influence on the military and replace those who were loyal to his father’s regime with his own hand-picked acolytes.

“Kim is phasing out the older generation of officers and he has learned that you have to manage your dictatorship carefully if you want to stay in power,” Daniel Pinkston, a North Korea analyst with The International Crisis Group in Seoul, told The Daily Telegraph.

“He is gradually phasing out the people who potentially pose the greatest threat to his hold on power, and that would include professional military officers who have commanded lots of troops in the field,” he said.

Mr Kim is replacing officers who had been appointed by his father, Kim Jong-il, with younger men who he hopes will now shore up his political power base, Pinkston said.

“He hopes that by appointing these men it will make them beholden to him,” he said. “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.”

The replacement of the head of the North Korean army comes after the more violent termination of a dozen female singers and musicians for reportedly making and selling pornographic videos.

The women apparently included Hyon Song-wol, Kim’s former girlfriend and a singer with the Unhasu Orchestra. Reports in China and South Korea say the women were machine-gunned in front of their relatives, who were then sent to labour camps.

North Korea meanwhile has cancelled a planned trip for a US envoy to travel to Pyongyang to seek the release of Kenneth Bae, an imprisoned missionary.