SEOUL (Reuters) - North Korean leader Kim Jong-il, thought to be recovering from serious illness, has picked his third and youngest known son to succeed him, a South Korean news report said on Thursday.

Supreme Commander of North Korean People's Army (front) waves as he visits the 2200 military unit to see military training at an undisclosed place in North Korea, in this undated picture released by KCNA November 5, 2008. REUTERS/KCNA

The demise of the 66-year-old Kim without a clear successor could likely add to the uncertainty of a country trying to develop nuclear weapons but with an economy in ruins and a population constantly on the edge of famine.

The question of succession in the secretive communist state is so closely guarded that no-one outside Kim’s immediate circle of family and confidants is thought to have any clear knowledge of the situation.

But speculation about his health and the succession is a favorite topic in South Korea.

“We believe Chairman Kim Jong-il has picked the son Jong-un he had with third and late wife Ko Yong-hui and given instructions to the Workers’ Party Organization and Guidance Department around January 8,” Yonhap news agency quoted an intelligence source as saying.

ANOINTED LEADER

Senior officials of the powerful party apparatus, where Kim himself began his training as anointed leader before succeeding his father in 1994, have been instructed to pass the message down the ranks, the source was quoted as saying.

South Korea’s spy agency said despite various reports over the question of succession in the North, nothing has been confirmed.

The Swiss-educated Jong-un is believed to have been born in late 1983 or early 1984 and has been described as his father’s favorite and an intelligent and thoughtful man.

But his youth has often been cited as a barrier to his rise to power in a society where the tradition of seniority is strong.

Media reports have portrayed Kim’s eldest son Jong-nam, in his late thirties and seen in file footage as overweight and unkempt, as out of favor. They say the second, Jong-chol, is considered by his father as too weak to take over power.

Yonhap said Jang Song-taek, Kim’s brother-in-law and a senior party official would act as the young Kim’s guardian.

Former South Korean President Kim Dae-jung, who held the first summit meeting with the North’s leader in 2000, said on Thursday that one of the three sons was likely to be installed as symbolic leader, with a cabinet of officials from the military and the party forming a collective leadership.

Experts said there have also been no signs to suggest that Kim is losing his grip on power, despite persistent rumors of his ailing health that began when he failed to appear at what was expected to be a triumphal military parade in September.