SEOUL, South Korea - North Korean leader Kim Jong-il has asked his country's overseas missions to pledge loyalty to his youngest son, signalling he has been anointed as next leader of the communist dynasty, a newspaper report said on Tuesday.

Kim, 67, is thought to have suffered a stroke in August. Analysts have said the North's recent military actions, including a nuclear test last week, may be aimed at helping him solidify power so that he can name a successor.

"It has been confirmed through various channels that North Korea sent emails to legations overseas, asking them to pledge their loyalty to (youngest son) Kim Jong-un," the South Korean daily Dong-A Ilbo reported an "informed source" as saying.

Analysts have said succession is one of the most closely guarded secrets in the highly secretive North, with Kim's plans only known to his small inner circle.

The paper quoted another informed source as saying: "North Korean leadership is educating senior officials at major security authorities with an emphasis on the justification of father-to-son succession over three generations."

The sources concluded these signs pointed to Jong-un being officially anointed.

Kim Jong-il, groomed for decades to take over the country from his father and state founder Kim Il-sung, has three sons but they are unknown to most North Koreans.

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 the three.

Even by North Korea's opaque standards, very little is known about the son, whose youth is also a potential problem in a society that adheres closely to the importance of seniority. -Reuters

(Reporting by Jon Herskovitz and Kim Junghyun; Editing by Jonathan Thatcher)