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.