Seoul: South Korea's ruling People Power Party decided on Thursday to oppose moves to impeach President Yoon Suk Yeol over his sudden decision, rescinded within hours, to declare martial law, the Yonhap news agency reported. South Korean opposition lawmakers were poised in the early hours of Thursday morning to formally introduce a motion to impeach Yoon over the decision, which had divided Yoon's ministers and unleashed six hours of political chaos in South Korea.

The opposition needs around eight members of the ruling party to break ranks and support the move. If successfully introduced to parliament, lawmakers could vote on the bill as early as Friday.

If the impeachment bid is passed and upheld by the constitutional court, Yoon would be the second South Korean president to have been impeached since massive candlelit protests against an influence-peddling scandal led to the removal of former president Park Geun-hye in 2017.

Yoon's declaration of martial law late on Tuesday attempted to ban political activity and censor the media in South Korea, which has Asia's fourth largest economy and is a key US ally. He told the nation in a television speech late on Tuesday that martial law was needed to defend the country from pro-North Korean anti-state forces, and protect the free constitutional order, although he cited no specific threats.

Within hours, South Korea's parliament, with 190 of its 300 members present, unanimously passed a motion for martial law be lifted, with 18 members of Yoon's party present. The president then rescinded the declaration of martial law, around six hours after its proclamation.

Protesters outside the National Assembly shouted and clapped. "We won!" they chanted, and one demonstrator banged on a drum. 

"There are opinions that it was too much to go to emergency martial law, and that we did not follow the procedures for emergency martial law, but it was done strictly within the constitutional framework," a South Korean presidential official told Reuters by telephone.

There has been no reaction yet from North Korea to the drama in the South. Yoon was embraced by leaders in the West as a partner in the US led effort to unify democracies against growing authoritarianism in China, Russia and elsewhere.

The National Assembly can impeach the president if more than two-thirds of lawmakers vote in favour. A trial by the constitutional court follows, which can confirm the motion with a vote by six of the nine justices.Yoon’s party has 108 seats in the 300-member legislature. If Yoon resigned or was removed from office, Prime Minister Han Duck-soo would fill in as leader until a new election was held within 60 days.