South Korea's President Yoon Suk-yeol impeached over martial law order

South Korea's Constitutional Court on Friday unanimously voted to uphold the impeachment of President Yoon Suk-yeol — removing the beleaguered leader from office four months after he thrust the country into political chaos following an ill-fated martial law order.

Thousands gathered at a rally in Seoul broke out in cheers over the decision, which marks a dramatic fall for Yoon, once a former star prosecutor who became president a barely a year after entering politics.

The court’s acting chief Moon Hyung-bae said the court acted based on Yoon's declaration of martial law around four months ago.

Yoon's decision to declare martial law — despite South Korea not facing any obvious security threat — thrust the country into political chaos. The former leader deployed hundreds of soldiers to parliament as opposition lawmakers attempted to vote down the martial law decree.

His martial law order only lasted six hours, but left behind a political crisis that rattled financial markets and unsettled the country's diplomatic partners.

Yoon not only acted dubiously by declaring martial law, but also violated the constitution by mobilising military and police forces to "obstruct the exercise of legislative authority", Moon said.

His removal triggers fresh presidential elections, which must be held within two months.

Yoon said in a statement issued via his defence team that he felt great regret for failing to live up public expectations.

He added that it was a “great honour to be able to work for the Republic of Korea."

Yoon defended his martial law order in his final hearing as a desperate attempt to draw public support against the "wickedness" of the opposition Democratic Party, which he said obstructed his agenda, impeached top officials and slashed the government's budget.

Without presidential immunity Yoon could now face other criminal charges, such as abuse of power.

Surveys indicate that the leader of the main liberal opposition Democratic Party, Lee Jae-myung, is an early favourite to win a by-election to be Yoon's successor. Lee himself is facing trials for corruption, amongst other offences.