An opposition-led motion to impeach South Korean President Yoon Suk Yeol over his brief declaration of martial law failed on Saturday as it did not meet the required quorum after his party boycotted the vote.

"With a total of 195 votes, the number of members who voted did not reach the required two-thirds majority of the total members. Therefore, I declare that the vote on this matter is not valid," National Assembly speaker Woo Won-shik said.

Opposition parties, which hold 192 seats in the 300-seat parliament, earlier filed the impeachment motion, which needed 200 votes to pass and went to the vote on Saturday evening.

But almost all 108 members of Yoon's People Power Party (PPP) filed out of the chamber before the vote, prompting critical shouts from the opposition -- with one yelling "Where are you going?" and others calling them "accomplices to insurrection".

Only three PPP members cast ballots.

Meanwhile, nearly 150,000 people were estimated by police to have filled the streets around the National Assembly, demanding that lawmakers impeach Yoon for his sudden imposition of martial law four days earlier, which plunged South Korea into turmoil.

For hours, people poured into the area around parliament where on Tuesday night soldiers were helicoptered in as part of Yoon's short-lived bid to subvert civilian rule.

Before the vote, Yoon, 63, apologised for the turmoil but said he would leave it to his party to decide his fate. (Agencies)