A South Korean man watches TV news about the alleged dismissal of Jang Song-Thaek, North Korean leader Kim Jong-Un's uncle, Seoul on December 3, 2013.

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 Defense 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).