Impeached South Korean President Yoon Suk Yeol attended court for the first time on Saturday to fight a request by investigators to extend his detention as they probe his failed martial law bid.

Thousands of Yoon’s supporters rallied outside the court and scuffled with police as they chanted support for the suspended leader, who plunged South Korea into its worst political chaos in decades with his bid to suspend civilian rule.

The president’s December 3 martial law declaration lasted just six hours, with lawmakers voting it down despite him ordering soldiers to storm parliament to stop them. He was impeached soon after.

Yoon was detained in a dawn raid on Wednesday in a criminal probe on insurrection charges after he refused investigators’ summons and went to ground in his residence, using his presidential security detail to resist arrest.

South Korea’s first sitting president to be detained, Yoon also declined to cooperate during the initial 48 hours detectives were allowed to hold him.

However, the disgraced president remains in custody after investigators requested a new warrant on Friday to extend his detention.

Yoon “explained and answered faithfully regarding the facts, evidence, and legal issues”, his lawyer Yoon Kab-keun told reporters after the hearing.

The court must decide whether to free Yoon, which analysts say is unlikely, or extend his detention for around another 20 days. Its ruling is expected late on Saturday or early Sunday.

Crowds of Yoon’s backers gathered outside the court, waving flags and holding “release the president” placards. Yonhap said police estimated about 12,000 supporters had rushed to the area.

Sixteen protesters were arrested after attempting to force their way into the courthouse, AFP reporters at the scene saw.

The hearing concluded after about five hours at around 6:50 pm (0950 GMT), a court official told AFP.

Yoon left the court in a blue Justice Ministry van with his guards jogging alongside, AFP reporters saw, heading back to the Seoul Detention Center where he is being held.

Two vehicles carrying staff from the Corruption Investigation Office, which is probing Yoon, were attacked by protesters “resulting in a threatening situation for the CIO personnel,” it said in a statement.

The body will “request that the police (impose) strict punishment based on the evidence collected regarding these actions.”

Yoon sent a letter through his lawyers on Friday thanking his supporters, who include evangelical Christians and right-wing YouTubers, for protests that he deemed “passionate patriotism”.

During the hearing some protesters outside chanted “Cha Eun-gyeong is a commie!”, referring to the judge reviewing the arrest request. Others cried “We love you, President Yoon Suk Yeol” and “Impeachment is invalid!”

They marched while waving South Korean and American flags and took over the main roads in front of the court. Yoon’s party typically favors South Korea’s US security alliance and rejects engagement with the nuclear-armed North.

“The likelihood of the court approving the arrest is very high and, aware of this, Yoon has urged maximum mobilization among his hardline supporters,” Chae Jin-won of Humanities College at Kyung Hee University told AFP.

“Today’s protests serve as a sort of farewell event between Yoon and his extreme support base.”

The crisis has seemingly boosted support for the conservative People Power Party (PPP), for whom Yoon won the presidential election in 2022.

A Gallup survey published on Friday showed the PPP’s approval rose to 39 percent, three points higher than the opposition Democratic Party.

A decision by the court to approve Yoon’s continued detention would give prosecutors time to formalize an indictment for insurrection, a charge for which he could be jailed for life or executed if found guilty.

Such an indictment would also mean Yoon would likely be detained for a maximum six months during the trial.

Once “the warrant is issued this time, (Yoon) will likely be unable to return home for an extended period”, political commentator Park Sang-byung told AFP.

Yoon said on Wednesday he had agreed to leave his compound to avoid “bloodshed” but that he did not accept the legality of the investigation.

He has refused to answer investigators’ questions, with his legal team saying Yoon explained his position the day he was arrested.

Yoon has also been absent from a parallel probe at the Constitutional Court, which is considering whether to uphold his impeachment.

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

He did not attend the first two hearings this week but the trial, which could last months, will continue in his absence.