South Korea's constitutional court has begun impeachment proceedings against President Yoon Suk Yeol, who was ousted for declaring martial law and looting his country. political turmoil.

MPs voted to impeach Yoon last Saturday, after his actions sparked widespread protests calling for his resignation.

The court now has six months to decide whether Yoon should be removed or returned.

Yoon's ruling People Power Party (PPP) has been grappling with the fallout ever since, with its leader announcing his resignation on Monday.

Although public hearings for Yoon's impeachment trial could take months, the court is under pressure to decide quickly and end political uncertainty. Activists have vowed to uphold their calls for Yoon's removal during the trial.

In the two previous instances where the president of South Korea faced impeachment, the court reversed one decision and upheld the other.

There had been questions as to whether the trial could proceed in Yoon's case, as the court currently only has six judges out of nine. Three of them retired recently and have yet to be replaced.

But the court said Monday that it could run Yoon's trial with just six judges, and set a preliminary hearing date for December 27.

If the court upholds impeachment in Yoon's case, the country must hold new presidential elections within 60 days. In the meantime, Prime Minister Han Duck-soo is acting president.

It is unclear whether Yoon will take the stand himself at court hearings.

He refused a summons to meet with prosecutors in Seoul on Sunday, and is expected to be ordered back in for questioning. If he does not come forward this week, the police may move to arrest him.

Yoon has defended his decision to impose martial law, and after his dismissal he is again he said he would fight to the end.

Minutes after the constitutional court convened on Monday morning, PPP leader Han Dong-hoon announced his resignation.

"I sincerely apologize to everyone who is suffering from this emergency situation," Han said in a televised press conference.

Han has been facing increasing calls for his resignation especially from the large pro-Yoon faction of his party, following the impeachment of the president.

At first Han had tried to arrange an orderly exit for Yoon. But when it became clear that Yoon was not supporting him, Han makes a face about it and calls him fired, saying that's the only way to get him fired.

On Saturday, 12 PPP lawmakers were believed to have voted for impeachment, allowing the motion to pass. But most other PPP lawmakers voted against Yoon's impeachment.

Five members of the Supreme Council of the PPP said after the vote that they would resign - which automatically dissolves the leadership of the party.

Since the Supreme Council has been "destroyed", Han said, it was now "impossible" to fulfill his duties as party leader.

"Although it pains me to think of my heartbroken supporters, I have no regrets," Han said, referring to his decision to call for Yoon's impeachment.