South Korean President Yoon Suk Yeol has accepted the resignation of Defense Minister Kim Yong-hyun and nominated his ambassador to Saudi Arabia, Choi Byung-hyuk, as new defense minister, Yonhap news reported on Thursday.

Yoon's office confirmed the nomination of Choi, a former army general, for the office.

Yoon's chief of staff, Chung Jin-suk, called Choi "a person of principle who carries out his duties with dedication and adheres to regulations," Yonhap reported.

Kim has been reported as having advised Yoon to declare martial law on Tuesday, which was lifted after a parliament vote demanding Yoon reverse it.

The nomination is the first official move by Yoon after he announced the withdrawal of the martial law declaration in the early hours of Wednesday, amid a storm of political turmoil and diplomatic fallout.

Parliament introduced a motion early on Thursday to impeach him over the botched attempt to impose martial law, but his party vowed to oppose the move, throwing the process into doubt.

The main opposition Democratic Party has called Yoon's martial law attempt a treasonous act, and its lawmakers could lead a vote for the bill as early as Friday.

U.S. officials said they were caught completely off guard by Yoon's martial law declaration, which Deputy Secretary of State Kurt Campbell said was "badly misjudged."