South Korean prosecutors have arrested former Defense Minister Kim Yong-hyun for his alleged involvement in President Yoon Suk Yeol’s martial law declaration earlier this week, according to local media reports.

Kim, who resigned on Wednesday, is widely regarded as a key figure in the brief martial law declaration issued on Tuesday. A senior military official and opposition members filing for Yoon’s impeachment claimed that Kim had proposed the martial law measure to the president.

President Yoon narrowly survived an impeachment vote in parliament on Saturday, following the controversial declaration. However, the leader of his own party warned that Yoon would ultimately need to step down.

Protests and investigations

The prosecution’s special investigative team questioned Kim after he voluntarily appeared at the Seoul Central District Prosecutors’ Office around 1:30 a.m. on Sunday, according to Yonhap News Agency.

Prosecutors have also imposed a travel ban on Kim and conducted raids on his official residence and office. 

Meanwhile, three minority opposition parties filed treason charges against Yoon, Kim, and martial law commander Park An-su. The police are also investigating allegations of treason against Yoon and senior officials.

Yoon’s apology

Before the vote, Yoon, 63, delivered a public apology for the crisis but left the decision regarding his fate to his party.

"I caused anxiety and inconvenience to the public. I sincerely apologize," Yoon said during a televised address, marking his first public appearance in three days.

He added that he would "entrust the party with measures to stabilize the political situation, including my term in office."

PPP lawmakers largely supported Yoon, even as party leader Han Dong-hoon—allegedly on an arrest list during Tuesday’s events—called for the President's resignation.

The political crisis

On Tuesday night, Yoon shocked the nation by granting the military extensive emergency powers, stating the move was necessary to combat “anti-state forces” and obstructive political opponents. However, he rescinded the decree six hours later after parliament, defying military and police blockades, voted unanimously to overturn it.

The martial law declaration plunged South Korea—Asia’s fourth-largest economy and a crucial US military ally—into its most severe political crisis in decades, raising concerns about the country’s future.