SEOUL (Kyodo) -- A South Korean court on Thursday decided the ongoing detention of President Yoon Suk Yeol is legally grounded, local media reported, a move that could lead investigators to seek a formal arrest warrant on suspicion that he incited insurrection.

The Seoul Central District Court made the judgment after Yoon's defense team asked it to review the legality of detaining the president, who faces the allegation over his declaration of martial law last month.

The court convened a session the same day to examine whether it is appropriate for a sitting president to be put under the control of the authorities, but Yoon declined to appear.

His defense team said he will refuse further questioning at the headquarters of the country's anti-corruption body, according to local media reports, a day after he was taken into custody.

The president "fully explained his position" on Wednesday, one of his lawyers was quoted by Yonhap News Agency as saying. He underwent questioning after being transported to the Corruption Investigation Office for High-ranking Officials, which is leading the probe into his short-lived imposition of martial law on Dec. 3.

The office had planned to resume its questioning of Yoon on Thursday morning.

The time spent for the court's review is not considered part of the 48 hours that investigators have from the beginning of detention to request an arrest warrant, according to Yonhap.

Yoon's presidential authority has been suspended since Dec. 14, when parliament passed an impeachment motion submitted by opposition parties accusing him of failing to meet constitutional requirements when he declared martial law.

On Thursday, the nation's Constitutional Court held its second hearing on Yoon's impeachment as planned, despite the request for postponement from his team of lawyers.

The court designated the witnesses, including former Defense Minister Kim Yong Hyun, who is suspected of having played a key role in Yoon's imposition of the decree, and scheduled additional hearings for Feb. 6, 11 and 13, the news agency said.

The court has 180 days from Dec. 14 to decide whether to approve Yoon's impeachment or reinstate him.