South Korea's Constitutional Court said on Monday that it was holding its first meeting on President Yoon Suk Yeol's impeachment case that same day, with all six of its judges participating.

After parliament voted for the investigation on Saturday, it falls to the court to decide whether to remove Yoon from office or reinstate him. 

Yoon is being investigated following his short-lived attempted imposition of martial law on December 3.

Lawmakers voted this down within a matter of hours, even as military personnel tried to enter the National Assembly. 

Yoon's presidential powers are suspended pending the verdict.

The court has up to six months to reach a decision but past cases in 2016 and 2004 were resolved much more quickly.

If Yoon is dismissed, an election would have to follow within 60 days.

Yoon wanted for questioning on Wednesday

A joint investigative team involving police, an anti-corruption agency and the Defense Ministry said it plans to ask Yoon's office that the president appear for questioning on Wednesday, as they expand a probe into whether his failed attempt to suspend parliamentary activity amounted to rebellion.

It's not clear whether the president will grant the request for an interview, with him and his office uncooperative with investigators in several related incidents so far.

Yoon has defended his martial law decree as a necessary act of governance against the main liberal opposition Democratic Party, calling its members "anti-state forces" bogging down his policy agenda. He has struggled to pass a budget and other legislation given the opposition's strength in parliament. 

Hundreds of thousands of people, both supporters and opponents of the president, took to the streets of Seoul over the weekend amid the impeachment vote in the National Assembly. 

Opposition leader calls for swift hearing

Democratic Party leader Lee Jae-myung urged the Constitutional Court to reach a resolution swiftly and recommended a special council for cooperation between the government and parliament. 

Lee lost the March 2022 presidential election by less than 1 percentage point of the popular vote. 

Yoon's conservative People Power Party (PPP) however criticized this proposal, saying it was an inappropriate attempted power grab from the opposition. 

PPP leader quits, in sign of rift over Yoon's move

The PPP has been divided by Yoon's December 3 mobilization of the military, with some members supporting the move and others opposing it. 

This became yet more visible on Monday, when party leader Han Dong-hoon announced his resignation in Seoul.

Han had publicly backed the bid to impeach Yoon, despite criticism from some party allies, but said he had no regrets.

"If martial law had not been lifted that night, a bloody incident could have erupted that morning between the citizens who would have taken to the streets and our young soldiers," Han told a news conference. 

What happened on December 3? 

In a surprise late-night TV address soon before midnight, Yoon became the first South Korean president in more than four decades to declare martial law. 

The move harkened back to a period of authoritarian leaders not seen in South Korea since the 1980s. 

Soldiers were dispatched to parliament to try to shut it down. 

But within hours, parliamentarians voted unanimously to rescind martial law again, albeit with only around 60% of them present. 

Soldiers and police subsequently withdrew again after this vote. 

No major violence occurred.

Foreign allies, not least the US, expressed relief and also surprise in the aftermath, praising the resilience of Seoul's democratic institutions. 

msh/sri (AFP, AP, Reuters)