Seoul, South Korea - South Korean President Yoon Suk Yeol faced demands to resign on Wednesday after his short-lived attempt to impose martial law was voted down by lawmakers and brought thousands of protesters to the streets.

Yoon's shock bid to impose martial law on South Korea for the first time in over four decades plunged the country into the deepest turmoil in its modern democratic history and caught its close allies around the world off guard.

The US, which stations nearly 30,000 troops in South Korea, initially voiced deep concern at the declaration, then relief that martial law was over.

The dramatic developments have left the future of Yoon – a conservative politician and former star public prosecutor who was elected president in 2022 – in jeopardy.

North Korea South Korean president declares martial law and cites North Korean "threats" in dramatic move

South Korea's main opposition party – whose lawmakers jumped fences and tussled with security forces so they could vote to overturn the law – demanded Yoon's immediate resignation.

"We will file charges of insurrection," against Yoon, his defense and interior ministers and "key military and police figures involved, such as the martial law commander and the police chief," the Democratic Party said in a statement.

It added that it would also push for impeachment.

The nation's largest umbrella labor union called an "indefinite general strike" until Yoon resigned.

And the leader of Yoon's own ruling party described the attempt as "tragic" while calling for those involved to be held accountable.

Yoon stunned the world with a late-night television announcement that he was declaring martial law, citing the threat of North Korea and "anti-state forces."

More than 280 troops backed by 24 helicopters arrived at parliament to lock down the site after the extraordinary declaration.

But 190 lawmakers defied the rifle-carrying soldiers to force their way into parliament to vote against the move, leaving Yoon with no choice but to retract. Under the constitution, martial law must be lifted when a majority in parliament demands it.

World South Koreans stage day of rage after martial law debacle: "The president is crazy"

"Just a moment ago, there was a demand from the National Assembly to lift the state of emergency, and we have withdrawn the military that was deployed for martial law operations," Yoon said in a televised address around 4:30 AM. "We will accept the National Assembly's request and lift the martial law through the Cabinet meeting."

Senior aides working for Yoon offered Wednesday to resign en masse over the martial law declaration.

By midday, Yoon had yet to reappear publicly.

The U-turn prompted jubilation among protesters outside parliament who had braved freezing temperatures to keep vigil through the night in defiance of Yoon's martial law order.

Demonstrators who had been waving South Korean flags and chanting "Arrest Yoon Suk Yeol" outside the National Assembly erupted in cheers.

Lim Myeong-pan (55) told AFP that Yoon's decision to rescind martial law did not absolve him of wrongdoing.

"Yoon's act of imposing it in the first place without legitimate cause is a serious crime in itself," Lim told AFP. "He has paved his own path to impeachment with this."

With more protests expected, large numbers of police were patrolling key avenues Wednesday morning.

Yoon had given a range of reasons to justify his action.

"To safeguard a liberal South Korea from the threats posed by North Korea's communist forces and to eliminate anti-state elements plundering people's freedom and happiness, I hereby declare emergency martial law," Yoon said in a televised address.

Yoon did not give details about the North's threats, but the South remains technically at war with nuclear-armed Pyongyang.

"Our National Assembly has become a haven for criminals, a den of legislative dictatorship that seeks to paralyze the judicial and administrative systems and overturn our liberal democratic order," Yoon claimed.

The president labeled the main opposition Democratic Party, which holds a majority in the 300-member parliament, "anti-state forces intent on overthrowing the regime."

Yoon and his People Power Party are also bitterly at odds with the opposition over next year's budget.

Opposition MPs last week approved a significantly downsized budget plan through a parliamentary committee.

Yoon's move came after his approval rating dropped to 19% in the latest Gallup poll last week, with many expressing dissatisfaction over his handling of the economy and controversies involving his wife, Kim Keon Hee.

Democratic South Korea is a major ally of the US in Asia, but Washington said it was not given advance notice of Yoon's plan to impose martial law.

"We welcome President Yoon's statement that he would rescind the order declaring emergency martial law," US Secretary of State Antony Blinken said.

"We continue to expect political disagreements to be resolved peacefully and in accordance with the rule of law."

China, a key ally of North Korea, urged its nationals in the South to stay calm and exercise caution, while Tokyo said it was monitoring the situation with "exceptional and serious concerns."

Vladimir Tikhonov, professor of Korea studies at the University of Oslo, said Yoon's move to impose martial law was "an attempt to wind history back."

"I don't think South Korea's civil society can recognize Yoon as a legitimate president any longer," he told AFP.