S Korea's Yoon apologises for martial law order ahead of impeachment vote

South Korea's president has said he's "very sorry" for causing public anxiety and inconvenience with his declaration of martial law earlier this week, and promised not to make another attempt to impose it.

President Yoon Suk-yeol made a public apology on Saturday, hours ahead of a parliamentary vote on a motion to impeach him and major protests calling for his departure.

"I sincerely apologise to the citizens who were greatly distressed," Yoon said. "I will leave it up to our party to stabilise the political situation in the future, including my term of office."

Yoon said he won't shirk legal or political responsibility for the declaration, adding that he will follow the direction of his party to resolve the political crisis caused by his move.

Yoon stunned the nation and the international community on Tuesday night by imposing martial law for the first time since the 1980s and deploying troops and helicopters to parliament.

But lawmakers managed to vote down the decree, forcing Yoon to rescind the order in the early hours of Wednesday in a night of extraordinary drama for a country assumed to be a stable democracy.

Yoon has gone to ground since and his scheduled address at 10:00 am (0100 GMT) announced by his office will be the first time he has spoken in public.

It comes ahead of a vote in parliament expected in the early evening on his possible impeachment.

Police have said they expect tens of thousands of anti-Yoon protestors to take to the streets ahead of the vote, with organisers hoping 200,000 people will attend.

Yoon dubbed 'significant risk'

The opposition bloc holds 192 seats in the 300-strong parliament, while Yoon's People Power Party (PPP) has 108.

A successful vote would suspend Yoon from office pending a ruling by the Constitutional Court.

PPP head Han Dong-hoon had initially said he would oppose the motion, but on Friday, he said Yoon had to go.

If Yoon remains, "there is a significant risk that extreme actions similar to the martial law declaration could be repeated, which could put the Republic of Korea and its citizens in great danger," Han said.

Han's U-turn was "significantly influenced by the gravity of the situation, particularly the mobilisation of intelligence agencies to arrest politicians," Shin Yul, a political science professor at Myongji University, told the AFP news agency.

However, late Friday, PPP spokesperson Shin Dong-uk said there had been "no mention" of changing the party's stance on opposing the impeachment motion during an emergency general party meeting.

An opinion poll released on Friday put backing for the 63-year-old president at a record low of 13 percent.