Kim Jong Un, 25, the youngest son of the North Korean dictator Kim Jong Il, has been formally declared as his successor, the South Korean media reported yesterday in the latest sign of dramatic change in the isolated totalitarian state.

The North Korean Workers’ Party, the country’s token parliament and Cabinet, and its military command, were notified of the planned succession after the second nuclear test, according to the Yonhap news agency and two Seoul newspapers.

In a briefing to members of its parliament, the South Korean intelligence agency said that Kim Jong Un was being referred to as Commander Kim and a song praising his virtues has been composed, according to the Dong-A Ilbo newspaper.

The news seems to confirm that after a serious illness last summer, Kim Jong Il, 67, is preparing for his family’s continued rule. It is a desire to offset the atmosphere of insecurity and uncertainty created by this transition that has led Kim Jong Il to put on displays of confidence and strength such as the underground nuclear test, many North Korea watchers believe.

Times Archive, 1980: Pyongyang settles political succession

Kim Il Sung today named Mr Kim Jong Il, his son, as his political successor

• The Crown Prince of North Korea, 1980

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The Seoul media reported that North Korea had been mounting amphibious landing exercises in the Yellow Sea, the site of a disputed sea border with South Korea.

As well as preparing to test a long-range rocket with the potential to strike the US, the North was reported to be planning to launch three or four medium-range Rodong missiles towards Japan, according to Yonhap.

Outside the upper ranks of the Pyongyang elite, few North Koreans are aware of the existence of Kim Jong Un and it is likely to be some time before he is named publicly.

He was born in 1983 and is the youngest of three known sons of Kim Jong Il. His half-brother, Kim Jong Nam, is 37 or 38 and the son of his father’s first wife. In 2001 he was detained in Japan while trying to visit Tokyo Disneyland on a forged passport. He has been spotted in Paris, Beijing and Macau.

Kim Jong Un and his brother, Kim Jong Chul, 28, were born to Koh Young Hee, a Japanese-Korean dancer. Before her death in 2004 state media had begun referring to her as Respected Mother, hinting at a special place for her and her boys in the Kim personality cult.

All the sons were educated at the International School of Berne in Switzerland. According to Kenji Fujimoto, a Japanese who worked as a sushi chef to Kim Jong Il and knew the children well, it was obvious that Kim Jong Un would eventually take over. “The older brother, Jong Chul, had the warm heart of a girl,” he told The Times. “The younger prince, Jong Un, was a boy of inner strength.If power is to be handed over, then Jong Un is the best for it,” Mr Fujimoto said. “He has superb physical gifts, is a big drinker and never admits defeat.”

As a boy, Kim Jong Un drove a Mercedes-Benz with adapted pedals and seat, around the grounds of Kim Jong Il’s home and used to ask for Mr Fujimoto’s menthol cigarettes.

North Koreans are being urged to devote themselves to a 150-day battle to boost economic production. One possible scenario is that Kim Jong Un will be presented to the nation at the conclusion of this campaign in October, and that other national achievements, such as the nuclear and missile tests, will be framed as his triumphs.

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