South Korea President Yoon apologises to nation for martial law declaration ahead of impeachment vote

South Korean President Yoon Suk Yeol has apologised on Saturday for the confusion caused by his declaration of martial law and says he will let his party decide on his future position.

"I am very sorry and would like to sincerely apologise to the people who were shocked," Mr Yoon said.

"I will leave it up to our party to stabilise the political situation in the future, including my term of office."

Mr Yoon said that he would not impose martial law for a second time.

"There are rumours that martial law will be invoked again. Let me be clear. There will never be anything like a second martial law," he said.

Mr Yoon said he would not seek to avoid legal and political responsibility for his decision, which he said was born of desperation.

Mr 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 politicians managed to vote down the decree, forcing Mr 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.

Mr Yoon has gone to ground since and the national address is 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.

Korean people 'alert' following martial law declaration

Thousands of people are lining the road leading to the country’s National Assembly, protesting the president's actions and calling for his impeachment.

The mood feels more like a music festival, peppered with calls to "Impeach Yoon Suk Yeol".

High school student Seo Ja Un, 19, was in tears as she told the ABC how the events of the last few days had shaken her faith in the country's democracy.

"From now I hope no more politicians who sabotage human rights will lead this country," she said.

"People of this country will be alert to human rights and politics from now."

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

Impeachment requires at least eight votes from Yoon's own party

Impeaching Mr Yoon would require support from 200 of the National Assembly's 300 members. The opposition parties that jointly brought the impeachment motion have 192 seats combined.

That means they would need at least eight votes from Mr Yoon's People Power Party (PPP).

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

Opposition leader Lee Jae-myung said Mr Yoon's speech was "very disappointing" given widespread public demands for him to step down.

His speech "only exacerbates the sense of betrayal and anger among the citizens", he said.

He added that the only solution to the current political chaos was "the immediate resignation of the president or an early departure through impeachment".

Mr Yoon's resignation is inevitable, the head of his ruling party said on Saturday.

"The normal performance of the president's duties is impossible under the (current) circumstances, and an early resignation of the president is inevitable," PPP leader Han Dong-hoon told reporters.

However, late on 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 per cent.

ABC/Wires