South Korean President Yoon vows to 'fight to the end'

South Korean President Yoon Suk Yeol said he would "fight to the end" on Thursday as his own political party shifted closer to voting with the opposition to impeach him over his short-lived martial law order that threw the US ally into turmoil.

In a lengthy televised address the embattled leader of Asia's fourth-largest economy also claimed North Korea had hacked South Korea's election commission, throwing doubt on his party's landslide election defeat in April.

Yoon is hoping his political allies will rally to his support but this appeared less likely after his fiery address, with the leader of his ruling People Power Party (PPP) responding that the time had come for Yoon to resign or be impeached by parliament.

At least seven members of the party were expected to support a new impeachment motion with two members declaring publicly they will vote in favour. At least eight PPP votes are needed for the two-thirds majority required to impeach Yoon.

Yoon said the opposition was "dancing the sword dance of madness" by trying to drag a democratically elected president from power, nine days after his aborted attempt to grant sweeping powers to the military.

"I will fight to the end," he said. "Whether they impeach me or investigate me, I will face it all squarely."

His comments were the first since he apologised on Saturday and promised to leave his fate in the hands of his party.

The defiant reversal to now fight raised the possibility Yoon, a career prosecutor and a legal expert, may have decided to take his chances to the court, hoping to make a dramatic comeback.

That may prove to be an "utter mistake" and the result of the president listening to the advice of wrong people, Shin Yul, a Myongji University political science professor said.

"It appears that he just doesn't want to step down and is trying to hang in there as he still thinks he did the right thing," Shin said.

Yoon faces a second impeachment vote in parliament expected on Saturday, a week after the first one failed because most of the ruling PPP boycotted the proceedings.

A vote to impeach would send the case to the Constitutional Court, which has up to six months to decide whether to remove Yoon from office or reinstate him.

In the latest sign that Yoon is losing his grip on power, PPP leader Han Dong-hoon told a meeting of party members on Thursday that they should join the opposition to impeach the president.

Even so, the party remains deeply divided and Yoon continues to have the backing of some PPP lawmakers.

Underscoring the divisions, the party chose a member close to the president as its floor leader by a majority vote on Thursday. Kweon Seong-dong said after his selection the party's official policy remains opposing the impeachment.

The president is separately under criminal investigation for alleged insurrection over the Dec. 3 martial law declaration, which he rescinded hours later, sparking the biggest political crisis in South Korea in decades.

In comments that echoed his justification for declaring emergency rule in the first place, Yoon said the "criminal groups" that have paralysed state affairs and disrupted the rule of law must be stopped at all costs from taking over government.

He was referring to the opposition Democratic Party which has blocked some of his proposals and raised allegations of government wrongdoing, but he gave no evidence of criminal activity.

A member of the Democratic Party leadership, Kim Min-seok, said Yoon's address was a "display of extreme delusion" and called on members of the president's ruling party to vote to impeach him.