SEOUL, South Korea — Hours after South Korea’s impeached President Yoon Suk Yeol was formally arrested, triggering rioting by his supporters, his lawyers said Sunday that he remains defiant in his refusal to answer questions over the probe into his declaration of martial law last month.

Yoon was formally arrested early Sunday, days after being apprehended at his presidential compound in Seoul. He faces possible imprisonment over his imposition of martial law, which set off the country’s most serious political crisis since its democratization in the late 1980s.

Yoon’s arrest could mark the beginning of an extended period in custody, lasting months or more.

The decision to arrest Yoon ignited unrest at the Seoul Western District Court, where dozens of his supporters broke in and rioted, destroying the main door and windows. They used plastic chairs, metal beams and police shields that they managed to wrestle away from officers. Some were seen throwing objects and using fire extinguishers, destroying furniture and office machines, smashing glass doors and spraying water on computer servers.

They shouted demands to see the judge who had issued the warrant, but she had already left.

Hundreds of police officers were deployed and nearly 90 protesters were arrested. Some injured police officers were seen being treated at ambulance vans. The court said it was trying to confirm whether any staff members were injured and assess the damage to its facilities.

In a statement issued through lawyers, Yoon lamented that the court did not recognize the “just purpose” of his martial law decree but also urged his supporters to express their frustrations peacefully. He called on the police to adopt a lenient stance toward the protesters.

But hundreds of Yoon’s supporters continued to clash with police as they extended their rallies into the evening in front of Seoul’s Constitutional Court, which is holding separate deliberations on whether to formally remove the impeached president from office or reinstate him. At least three protesters were detained at the scene. There were no immediate reports of damage to the court, barricaded by police.

In granting law enforcement’s request for an arrest warrant for Yoon, the Seoul Western District Court said there was a threat he could destroy evidence. Yoon and his lawyers had appeared in the court Saturday and argued for his release.

The Corruption Investigation Office for High-Ranking Officials, which is leading a joint investigation with police and the military, can now extend Yoon’s detention to 20 days, during which they will transfer the case to public prosecutors for indictment.

Investigators are examining whether Yoon’s Dec. 3 martial law decree amounted to an attempted rebellion. While South Korean presidents have wide-ranging immunity from prosecution while in office, the protection does not extend to allegations of rebellion or treason.

Yoon’s lawyers could also file a petition to challenge the court’s arrest warrant. Yoon rejected a questioning set by investigators and stayed at a detention center.

Yoon’s defense minister, police chief and several top military commanders have been arrested and indicted for their roles in the enforcement of martial law.

The crisis began when Yoon, in an attempt to break through legislative gridlock, imposed military rule and sent troops to the National Assembly and election offices. The standoff lasted only hours after lawmakers who managed to get through a blockade voted to lift the measure. The opposition-dominated assembly voted Dec. 14 to impeach him, which left his political fate with the Constitutional Court.

Seok Dong-hyeon, one of Yoon’s lawyers, called the court order for his arrest “the epitome of anti-constitutionalism and anti-rule of law.” He pointed to the riot and said Yoon’s arrest would inspire more anger from his supporters.