South Korean authorities have imposed a travel ban on President Yoon Suk Yeol, who is under investigation for his short-lived martial law declaration last Tuesday.

Yoon narrowly survived an impeachment motion against him over the weekend, after MPs from his ruling People Power Party (PPP) boycotted the vote.

PPP members said they had decided not to support the motion after Yoon agreed to shorten his term and not get involved in foreign and domestic affairs.

However, the opposition Democratic Party, which commands a majority in the parliament have criticised the deal, with floor leader Park Chan-dae calling it "an illegal, unconstitutional second insurrection and a second coup".

Tens of thousands of people have come out in protest since Yoon's short-lived martial law order, calling for him to resign or be impeached.

Since then, despite the failed impeachment motion, several key figures involved in the martial law order have also seen action taken against them.

Former Defence Minister Kim Yong-hyun, who reportedly proposed the martial law declaration to Yoon, was arrested on Sunday. He had earlier resigned on Wednesday after apologising and saying he would take "full responsibility".

Travel bans have been placed on Kim, Lee, Defence Counterintelligence Commander Yeo In-hyung, and Army Chief of Staff Park An-su.

Many others have stepped down from their posts.

These include former Interior Minister Lee Sang-min who resigned on Sunday, saying he would take responsibility for "failing to serve the public and the president well".

And on Wednesday, senior aides of Yoon's office, including his chief of staff, tendered mass resignations hours after the martial law declaration was lifted.

Shortly after his political nemesis, President Yoon Suk Yeol, declared martial laylast Tuesday, Lee Jae-myung  livestreaming from his cellphone. While driving to the National assembly, the leader of South Korea’s main opposition party appealed to Koreans to rush to the assembly and hold back soldiers trying to seize the Parliament.

“You must protect the assembly, the last line of defense for our democracy,” Mr. Lee said repeatedly — in a watershed moment for South Korean democracy and for his own political career. Mr. Lee’s exhortation, relayed by YouTubers, helped attract crowds who slowed down the advance of troops and bought time for lawmakers to vote down Mr. Yoon’s martial law​ decree, forcing the president to withdraw it after just six hours​​.

Mr. Lee, who has been fighting legal charges that he says are politically motivated, now finds himself in a stronger political position than ever. His party holds the majority in the assembly and he represents what most South Koreans want: Mr. Yoon removed from office. Polls show he is most favored to win if a presidential election is held now.

With political turmoil still roiling around him, Mr. Lee looked calm and in control this week — and determined to oust Mr. Yoon quickly. But his party’s first attempt to impeach Mr. Yoon on Saturday, when the president’s party boycotted the parliamentary vote. Mr. Lee’s Democratic Party plans to organize an impeachment vote every Saturday.