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's eight justices 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.

The acting president, Han Duck-soo, will remain in office until South Koreans choose a new leader. Han vowed to ensure there were "no gaps in national security and diplomacy" and to maintain public order until the vote took place.

“Respecting the will of our sovereign people, I will do my utmost to manage the next presidential election in accordance with the constitution and the law, ensuring a smooth transition to the next administration,” he said in a televised address.

Yoon said in a message issued via his defence team that he felt great regret for failing to live up public expectations. It had been a “great honour" to serve as president, he added.

Whilst many celebrated the court's verdict, Yoon's supporters, gathered outside his residence cried and screamed when they saw Moon deliver the news on a televised screen. They waved South Korean and US flags and chanted slogans.

“Given the grave negative impact on constitutional order and the significant ripple effects of the defendant’s violations, we find that the benefits of upholding the constitution by removing the defendant from office far outweigh the national losses from the removal of a president,” Moon said. He added that Yoon's declaration had created chaos in all areas of South Korean society.

Without presidential immunity, Yoon now faces a separate criminal trial on charges of insurrection.

His party said it accepted the court's decision, which it described as "regrettable". "We extend our sincere apologies to the people," People Power party lawmaker Kwon Young-se said, according to local media.

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.