The department is the same branch of the North Korean government where Kim's father first began work in 1964.
The move has "decisive relations" to the transfer of power, a man said to be close to the younger Kim told the AP news agency.
The man, who was not named, said he had a close business relationship with the North Korean leader's son.
He said the younger Kim had "played a key role in North Korea" and his return after several years abroad means "he will proceed to the next step" in plans outlined for him, the man told AP.
South Korea's National Intelligence Service has not made any official comment on the reports.
|Kim Jong-nam was caught trying to enter |
Japan on a fake passport in 2001 [AFP]
Kim Jong-il has not yet publicly named an heir, prompting speculation about who might eventually take the helm and whether he will designate one of his sons as the next leader, continuing the world's only communist dynasty.
Kim Jong-il took over the leadership of North Korea following the death in 1994 of his father, Kim Il-sung, the founder of the country who remains designated "eternal president" despite his death.
The health of the current North Korean leader, like many aspects of life in the country, is a closely guarded secret.
Nonetheless there have been a series of reports that the elder Kim is suffering from heart disease and diabetes.
However, South Korean intelligence officials have also said recently that his health is not believed to be as bad as some media reported in recent months.
|Critics in South Korea are hoping for the |
end of the Kim regime [Reuters]
Kim Jong-nam was widely believed to have fallen out of favour in 2001 after he was caught entering Japan on a fake passport saying he wanted to visit Tokyo Disneyland.
The publicity – and ridicule- the case attracted was said to have embarrassed his father, and the younger Kim has since spent most of his time living in China and the gambling enclave of Macau.
However, the business associate contacted by AP said reports the issue had embarrassed the North Korean leader were fabricated by South Korean officials in an effort to discredit him as a possible future leader.
The younger Kim is the offspring of an unofficial relationship between Kim Jong-il and North Korean actress Sung Hae Rim, who died in Moscow in 2002.