South Korean President Yoon Suk Yeol on Saturday apologised for his attempt to impose martial law this week but did not resign, defying intense pressure to step down even from some in his ruling party and only hours ahead of a planned impeachment vote.

Yoon said he would not seek to avoid legal and political responsibility for his decision to declare martial law for the first time in South Koreainfo-icon since 1980. He said the decision was born of desperation.

The speech was the embattled leader's first public appearance since he rescinded the martial law order early on Wednesday, just six hours after it was declared and after parliament defied military and police cordons to vote against the decree."I am very sorry and would like to sincerely apologise to the people who were shocked," Yoon said in a televised address to the nation, during which he bowed.

"I leave it up to my party to take steps to stabilise the political situation in the future, including the issue of my term in office," he said.

Han Dong-hoon, leader of Yoon's People Power Party (PPP), said after the address that the president was no longer in a position to carry out public duty and his resignation was now unavoidable.

On Friday, Han said Yoon was a danger to the country and needed to be removed from power, increasing the pressure on Yoon to quit even though PPP members later reaffirmed a formal opposition to his impeachment.

Han was scheduled to meet Prime Minister Han Duck-soo on Saturday, local Yonhap News reported. Under the constitution if Yoon resigns or is impeached then the prime minister, who was appointed by Yoon, becomes South Korea's interim president.

Lawmakers will vote on the main opposition Democratic Party's motion to impeach Yoon later on Saturday.

Yoon shocked the nation late on Tuesday when he gave the military sweeping emergency powers in order to root out what he called "anti-state forces" and overcome obstructionist political opponents.