SEOUL — South Korea's impeached President Yoon Suk-yeol appeared at the Constitutional Court for the first time on Tuesday, and vowed to cooperate with the judges who will decide whether to remove him from office.

The country was plunged into political chaos by Yoon's Dec 3 martial law declaration, which lasted just six hours before lawmakers voted it down.

They later impeached him, stripping him of his duties. He also became the first sitting South Korean president to be arrested in a criminal probe on insurrection grounds.

Thousands of protesters — both for and against Yoon — flocked to the Constitutional Court, which is holding hearings to decide whether to uphold his impeachment.

"I will respond to any questions or provide further remarks if necessary," Yoon told the judge.

Yoon was asked during the hearing whether he had instructed top military commanders to "drag out "lawmakers from parliament to prevent them from voting down his martial law decree.

"No," he told the judge.

Court spokesperson Cheon Jaehyun told reporters that Yoon's legal team has requested to call "at least 24 individuals" as witnesses, including election-related officials.

Yoon, who remains head of state, is being held in a detention center pending a criminal probe on charges of insurrection.

Shortly after the hearing, the Corruption Investigation Office probing the martial law declaration said it had sent six investigators and a prosecutor to the detention center to question Yoon, who has been refusing to submit to their questioning.

However, the van escorting Yoon was seen traveling to a hospital in Seoul, instead of the detention center.

The Justice Ministry said Yoon went for "a medical treatment", based on results of a medical exam the previous day.

If the court rules against Yoon, he will lose the presidency and elections will be called within 60 days.

The prosecution lawyers, who were selected by the parliament, slammed the comments made by Yoon and his lawyers as "largely contradictory, irrational and unclear, making them entirely incomprehensible".

"If they continue to evade responsibility as they did today, it will only work against them in the impeachment trial and cause even greater disappointment among the public," they added.

Yoon stayed away from the first two hearings last week, but the trial, which could last months, will continue even if he is absent.

Yoon has also been refusing to submit to separate questioning by the Corruption Investigation Office, the body in charge of the criminal probe into his martial law declaration.

It said it had attempted to compel him to attend but because of the "suspect's continued refusal to cooperate", they abandoned the efforts.

On Saturday, Yoon attended a hearing at the Seoul Western District Court on whether to extend his detention. When it was extended, hundreds of pro-Yoon protesters attacked the court building and scuffled with police officers. Dozens were arrested.

'Riling public opinion'

The impeached president's decision to start showing up at the Constitutional Court hearing is more about inflaming his die-hard supporters than helping the judicial process along, legal expert Kim Nam-ju said.

"Whether it's the legal representative speaking or Yoon himself speaking, it's nearly the same — it's more about riling public opinion," Kim told AFP.

But whatever Yoon's motives, "from the perspective of the Constitutional Court judges, hearing directly from the defendant is far more significant", he said.

Kim added that Yoon's refusal to engage in the criminal investigation into his martial law declaration will not work in his favor overall, even if he continues showing up at the Constitutional Court.

"Refusing to comply with the warrant execution and declining to testify will gradually be considered as factors unfavorable to his case in the impeachment trial," said Kim.

"It shows they are not adhering to the legal framework."

Yoon has claimed the criminal probe is illegal and resisted arrest for weeks, vowing to "fight to the end".

Agencies Via Xinhua