Yoon's shock bid to impose South Korea's first martial law 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 United States, which stations nearly 30,000 troops in South Korea to protect it from the nuclear-armed North, initially voiced deep concern at the declaration, then relief that martial law was over.

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

South Korea's main opposition party -- whose lawmakers jumped fences and tussled with security forces so they could vote to overturn the law -- demanded that Yoon step down immediately over the attempted "insurrection".

The nation's largest umbrella labour union also 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 backed down after lawmakers voted to oppose the declaration, which he made late on Tuesday night citing the threat of North Korea and "anti-state forces".

"Just a moment ago, there was a demand from the National Assembly to lift the state of emergency, and we have withdrawn the military that was deployed for martial law operations," Yoon said in a televised address around 4:30 am (1930 GMT Tuesday).

"We will accept the National Assembly's request and lift the martial law through the Cabinet meeting."

Yonhap news agency then reported that Yoon's cabinet had approved the motion to lift the order.

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

By the start of the working day, Yoon had yet to reappear publicly.