By Jack Kim and Ju-min Park
SEOUL (Reuters) - North Korean leader Kim Jong Un is believed to have dismissed a powerful uncle, a man key to his rise to power, from his posts, South Korean lawmakers said on Tuesday, a move that could help consolidate his power base with a younger guard of aides.
Jang Song Thaek was likely sacked as vice chairman of the powerful National Defence Commission and as a department head of the ruling Workers' Party, lawmaker Jung Cheong-rae said, citing a senior South Korean official with the National Intelligence Service (NIS).
Analysts who watch the North's power structure say Jang's removal would not have been possible without the approval of the third Kim to rule in the family dynasty.
The move is likely to tip the balance in favor of another close aide - the top political operative for the army, which could mean a symbolic victory for the 1.2-million-strong military.
Choe Ryong Hae, director of the General Political Bureau of the Korean People's Army, has been the most prominent figure to accompany Kim at public events and is a reminder of the state's political roots in military power.
There was no immediate mention of Jang's fate on North Korea's KCNA news agency, the primary source of information on the impoverished country for outsiders and which regularly carries editorials threatening the wealthy, democratic South and the United States with destruction.
Two members of the South Korean parliament's Intelligence Committee told separate news briefings that the NIS had confirmed the public execution of two close aides to Jang in the North's ruling Workers' Party for corruption.
"The briefing by an NIS senior official was that they believe Jang Song Thaek has lost his posts," Jung, who is the ranking opposition member of the intelligence committee, said.
"Following (the executions), the NIS said it believes Jang Song Thaek has not been seen and has lost his posts," Jung told the briefing.
A ruling party member of the committee held a separate news briefing and delivered a similar report.
The removal of Jang, a key figure in the power transition following the 2011 death of Kim's father, Kim Jong Il, could tip the balance in the fiercely competitive group of confidants surrounding the current leader but was unlikely to impact on Kim Jong Un's hold on power, experts said.
WHAT HAPPENS TO ECONOMIC REFORMS?
"Jang Song Thaek is a person who at one point Kim Jong Un had to cut out as he solidifies his own power structure," said Koh Yu-hwan of Dongguk University in Seoul, a leading expert on the North's leadership.
"I think the young elite had Kim get rid of Jang, meaning that he will rule without a guardian."
Accordion-playing Jang, 67, is married to Kim Jong Un's aunt, Kyong Hui, who is a daughter of the North's founding leader and its "eternal President", Kim Il Sung.
Jang, who is widely seen as an advocate of economic reform, was purged in a power struggle in 2004 under Kim Jong Il's rule but was reinstated two years later.
The U.S. government was still trying to confirm the reports of a shake-up in Pyongyang.
A U.S. official said the report of Jang's dismissal "could well be true given that this is a man who ... has been purged and rehabilitated before, by Kim Jong Il, so there is a precedent."
Kim Jung-un, the source added, "has established himself as a ruthless leader unafraid to shuffle his inner deck when it suits him."
One key question now is what Jang's ouster will mean for the devastated economy.
"Within the current leadership, he (Jang) seems to be the face of economic reform, so there is a risk involved with removing someone that close to the program," said John Swenson-Wright, a senior fellow at Chatham House, a London-based international affairs think tank.
Earlier this year, Jang and his wife were seen backing the appointment of Pak Pong Ju, a career technocrat, for the post of premier to spearhead a push to improve the economy.
Jang has been the central figure among top officials and family members who worked to ensure the young and untested son of Kim Jong Il took over power when his father died in 2011.
While Jang's ouster could symbolically tip the balance of power in favor of a key figure in the military, such as Choe, analysts say it is unlikely to signal a return to the military grandstanding of Kim's father as a top priority.
Apart from domestic political problems, North Korea is involved in a protracted standoff with the West over its nuclear weapons program.
Tensions between North and South Korea soared earlier this year as Pyongyang reacted angrily to tightened U.N. sanctions imposed in response to its latest nuclear test, but then eased for several months. The two sides are still technically at war after their 1950-53 civil war ended in a truce, not a peace treaty.
(Additional reporting by James Pearson, Michelle Kim and Narae Kim in SEOUL and Warren Strobel in WASHINGTON. Editing by Nick Macfie and Dean Yates)