SEOUL • They used to call him the "Little General", but Mr Kim Jong Nam - once heir apparent to his father and North Korea's then leader Kim Jong Il - fell from grace in 2001 after a spectacular blunder.

Yesterday, after more than a decade in exile from the North, Mr Kim, the 45-year-old half- brother of current leader Kim Jong Un, was allegedly assassinated in Malaysia.

Born of his father's relationship with actress Sung Hae Rim, Mr Kim was known to have been a computer enthusiast, fluent Japanese speaker, and student in both Russia and Switzerland.

He lived in Pyongyang after finishing his overseas studies and was put in charge of overseeing North Korea's information technology policy.

But the eldest son of the supreme leader was already seen by Seoul experts as something of a political lightweight when, in 2001, he fell out of favour.

He was embarrassingly detained at a Tokyo airport trying to enter Japan to visit Disneyland on a false Dominican Republic passport, accompanied by two women and a child.

Mr Kim and his family afterwards lived in virtual exile in Macau, Singapore and China.

His half-brother Kim Jong Un took over as North Korean leader when their father died in December 2011.

In an e-mail exchange with a Japanese journalist published in 2012, Mr Kim spoke disparagingly of his half-brother, saying he lacked "any sense of duty or seriousness", and warned that bribery and corruption would lead to North Korea's eventual collapse.

In another exchange with the same reporter in 2012, Mr Kim said: "Anyone with normal thinking would find it difficult to tolerate three generations of hereditary succession."

Mr Kim had been targeted in the past. In October 2012, South Korean prosecutors said a North Korean detained as a spy had admitted involvement in a plot to stage a hit-and-run car accident in China in 2010 targeting Mr Kim.

That same year, a Moscow newspaper reported he was having financial problems after being cut off by the Stalinist state for doubting its succession policy.

The Argumenty i Fakty weekly said he was kicked out of a luxury hotel in Macau over a US$15,000 (about S$21,000) debt.

Mr Kim's son Kim Han Sol studied at a university in Paris, France. Back in 2012, when at an international school in Bosnia, he labelled his uncle a "dictator" in an interview.

"My dad was not really interested in politics," Mr Kim Han Sol told the interviewer when asked why his father was passed over for the dynastic succession in favour of his younger brother.

AGENCE FRANCE-PRESSE