North Korean leader Kim Jong-il has told top officials to pledge loyalty to his youngest son.
The move signals his anointment as heir to the family dynasty that has ruled since the state's founding.
Mr Kim, 67, is thought to have suffered a stroke in August which raised questions about his continued control.
Analysts have said North Korea's recent military grandstanding, including a nuclear test last week, may be aimed at helping him solidify power so he can name a successor.
North Korea has asked the country's main bodies and its overseas missions to pledge loyalty to Mr Kim's youngest son Kim Jong-un.
Kim Jong-un, born either in 1983 or early 1984, was educated in Switzerland and intelligence sources have said he appears to be the most capable of Mr Kim's three known sons.
Kim Jong-il was groomed for decades to take over from his father and state founder Kim Il-sung.
However, his three sons are unknown to most North Koreans, which would make the succession of any of them a daunting task.
