SEOUL (Reuters)

South Korean lawmakers on Saturday impeached President Yoon Suk Yeol over his failed martial law bid, with the opposition declaring a "victory of the people".

The vote took place as hundreds of thousands took to the streets of Seoul in rival rallies for and against Yoon, who launched a failed attempt to impose martial law on December 3.

Out of 300 lawmakers, 204 voted to impeach the president on allegations of insurrection while 85 voted against. Three abstained, with eight votes nullified.

With the impeachment, Yoon has been suspended from office while South Korea's Constitutional Court deliberates on the vote.

The court has 180 days to rule on Yoon's future.

If it backs his removal, Yoon will become the second president in South Korean history to be successfully impeached.

Prime Minister Han Duck-soo -- now the nation's interim leader -- told reporters he would "devote all my strength and efforts to ensure stable governance".

Two hundred votes were needed for the impeachment to pass, and opposition lawmakers needed to convince at least eight parliamentarians from Yoon's conservative People Power Party (PPP) to switch sides.

"Today's impeachment is the great victory of the people," opposition Democratic Party floor leader Park Chan-dae said following the vote.

'We, the people'

A Seoul police official told AFP at least 200,000 people had massed outside parliament in support of removing the president.

The Democratic Party said ahead of the vote that impeachment was the "only way" to "safeguard the Constitution, the rule of law, democracy and South Korea's future".

Yoon remained unapologetic and defiant as the fallout from his disastrous martial law declaration deepened and an investigation into his inner circle has widened.

Yoon Suk Yeol said he would "step aside", urging an end to "politics of excess and confrontation".

"Though I must now step aside for a while, the journey toward the future... must never come to a stop," he said in a televised address.