SEOUL — South Korean President Yoon Suk-yeol will not attend the first hearing of his impeachment trial this week because of safety concerns, his lawyer said on Sunday.

Yoon has been holed up in the presidential residence and protected by an elite guard force since being suspended and impeached last month, following a short-lived declaration of martial law that plunged the country into political chaos.

He has refused to meet prosecutors and investigators and his presidential guard unit thwarted an attempt to arrest him following a tense, hours-long standoff earlier this month.

The Constitutional Court has scheduled five trial dates spanning Jan 14 to Feb 4, which will proceed in his absence if he does not attend.

"Concerns about safety and potential incidents have arisen. Therefore, the president will not be able to attend the trial on Jan 14," lawyer Yoon Kab-keun said in a statement sent to AFP. "The president is willing to appear at any time once safety issues are resolved."

The court will decide whether to uphold his impeachment or restore him to office.

Separately, investigators seeking to question Yoon on insurrection charges linked to his ill-fated martial law declaration are preparing another arrest attempt.

His lawyers have repeatedly said an initial seven-day warrant and the new one they secured this week were both "unlawful".

Investigators have kept secret the length of the new warrant, with local media reporting it is longer than the previous one.

Yoon's supporters and opponents have gathered almost daily in Seoul since the crisis unfolded.

On Sunday, more demonstrations were planned by rival camps outside Yoon's residence and on the streets, either calling for his impeachment to be declared invalid or for him to be detained immediately.

The president's legal team said his guards were on "high alert".

A team of Corruption Investigation Office officials and police are planning for the next arrest attempt, which they said could be their last.

The CIO said anyone obstructing their attempt could be detained and police reportedly held a meeting of top commanders on Friday to plan for the renewed effort.

It said in a text message that Yoon's attorneys submitted a notice of appointment of lawyers on Sunday afternoon, without elaborating, Reuters reported.

Former Presidential Security Service chief Park Chong-jun, who resigned on Friday, faced two days of questioning and gave no explanations for his resignation.

"I am cooperating as diligently as possible with the authorities' investigation," he told reporters on Saturday.

His replacement, acting chief Kim Seong-hun, refused to turn up to a third summons on Saturday, claiming he had to protect Yoon, opening him up to possible arrest.

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