The development comes hours before the main liberal opposition Democratic Party submits a new motion to impeach Yoon as the country's main law enforcement institutions expand their investigation into whether the president's declaration amounted to rebellion. The first impeachment attempt failed last Saturday when the ruling party boycotted the vote. The Democratic Party said it aims to put the new motion to a vote on Saturday

Yoon's ill-conceived power grab has paralyzed South Korean politics, frozen its foreign policy, and rattled financial markets, greatly reducing his chances of completing his five-year term and casting a turbulent shadow over one of Asia's most robust democracies

After last week's impeachment motion fell through, the leader of Yoon's conservative party pledged to arrange his stable exit from power, saying the party will coordinate with Cabinet members over state affairs and that Yoon will be sidelined from duties during a transition to an early election

However, the plans have been widely criticized as unrealistic and unconstitutional. The constitution explicitly states that impeachment is the sole method for suspending presidential powers and that the authority to command the military rests solely with the president. The Defense Ministry said this week that Yoon remains in charge of the country's military forces

Earlier Wednesday, Yoon's former defense minister, Kim Yong Hyun, was arrested after a Seoul court approved a warrant for him on allegations of playing a key role in a rebellion and committing abuse of power. Kim became the first person arrested over the December 3 martial law decree

Police said National Police Agency Commissioner General Cho Ji Ho and Kim Bong-sik, head of the metropolitan police agency of the capital, Seoul, were being held at Seoul's Namdaemun police station

They have been investigated for their roles in deploying police forces to the National Assembly in an attempt to block lawmakers from entering the parliament to vote to lift Yoon's martial law decree, which was abruptly announced on the night of December 3

The Assembly was also encircled by heavily armed troops, which military commanders say were deployed on the orders of the former defense minister. But enough lawmakers eventually managed to enter a parliament chamber and unanimously rejected Yoon's decree, forcing the Cabinet to lift it before daybreak on December 4

During a parliamentary hearing Tuesday, Kwak Jong-keun, commander of the Army Special Warfare Command whose troops were sent to parliament, testified that he received direct instructions from Kim Yong Hyun to obstruct lawmakers from entering the Assembly's main chamber