Seoul (AFP) - Thousands of protesters marched on President Yoon Suk Yeol’s office in the South Korean capital Wednesday evening, joining a push by the country’s opposition to impeach the leader after his extraordinary but short-lived imposition of martial law.

Yoon’s shock bid to suspend civilian rule for the first time in over four decades – before being overturned by lawmakers in a night of drama – plunged South Korea into deep turmoil and alarmed its close allies.

The future of Yoon, a conservative politician and former star public prosecutor who was elected president in 2022, is now highly uncertain.

Live feed video showed thousands of protesters marching towards Yoon’s office in central Seoul after staging a rally in Gwanghwamun Square.

South Korea’s opposition parties – whose lawmakers jumped fences and tussled with security forces to vote down the martial law – filed a motion to impeach Yoon.

They were yet to decide when to put it to a vote, but it could come as soon as Friday.

The opposition holds a large majority in the 300-member parliament and needs only a handful of defections from the president’s party to secure the two-thirds majority needed to pass the motion.

The DP has also filed charges of “insurrection” against the president, some of his ministers and top military and police officials – which can carry a penalty of life imprisonment or even death.

The nation’s largest umbrella labour union called an “indefinite general strike” until Yoon resigns.

Even the leader of Yoon’s own ruling party described the attempt as “tragic” while calling for those involved to be held accountable.

Seoul’s stock exchange closed down more than one percent Wednesday as markets were roiled by the turmoil.

- Defiance -

In his late-night television announcement, Yoon declared martial law, citing the threat of North Korea and “anti-state forces”.

More than 280 troops, some flown in by helicopters, arrived at parliament to lock down the site.

But 190 lawmakers defied rifle-carrying soldiers to force their way into parliament to vote against the move.

This left Yoon with no choice but to retract his decision and call off the military in another television address six hours later.

Under the constitution, martial law must be lifted when a majority in parliament demands it.

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

Yoon’s defence minister also offered to step down, saying he took “full responsibility for the confusion and concern” around the martial law declaration.

By evening, Yoon had yet to publicly reappear.

- ‘Impeachment’ -

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

Demonstrator Lim Myeong-pan, 55, told AFP that Yoon now has to go.

“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.”

As night fell in Seoul, protesters gathered again, ramping up their calls for Yoon to go.

“I was so incensed I couldn’t sleep a wink last night, I came out to make sure we push out Yoon once and for all,” 50-year-old Kim Min-ho told AFP at a demonstration at the assembly Wednesday.

- ‘Anti-state’ elements -

Yoon had said that his imposition of martial law was 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”.

Yoon did not elaborate on the North’s threats, but the South remains technically at war with nuclear-armed Pyongyang.

The president labelled the main opposition Democratic Party “anti-state forces intent on overthrowing the regime”.

In recent weeks, Yoon and his People Power Party have been bitterly at odds with the opposition over next year’s budget.

His approval rating dropped to 19 percent in the latest Gallup poll last week, with voters angry at the state of the economy as well as controversies involving his wife, Kim Keon Hee.

Yoon’s action took allies by surprise, with the United States, which has nearly 30,000 troops in the country to protect it from the nuclear-armed North, saying it had no prior notice and voicing relief at his reversal.

“This is a surprising last-ditch move by Yoon to grab political power,” Gi-Wook Shin, a sociology professor at Stanford University, told AFP.

“This move will only fasten the demise of his political career as it is likely to lead to his impeachment.”