South Korea's suspended President Yoon Suk Yeol will not attend the first hearing of his impeachment trial next week due to safety concerns, his lawyer said on Sunday.

Yoon has been staying at the presidential residence, under the protection of an elite guard force, since his suspension and impeachment last month. His impeachment followed a brief declaration of martial law that caused political turmoil in the country.

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

The Constitutional Court has set five trial dates between January 14 and February 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 January 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 who want to question Yoon on insurrection charges related to his martial law declaration are preparing for another arrest attempt.

'High alert'
Yoon's legal team says his guards remain on "high alert."

If investigators succeed in detaining him, Yoon would become the first sitting South Korean president to be arrested.

If convicted, he faces prison or even the death penalty.

A team of investigators from the Corruption Investigation Office (CIO) and police are preparing for the next attempt, which they have indicated could be their last.

The CIO warned that anyone obstructing the attempt could be detained. Police reportedly held a meeting with top commanders on Friday to plan for the renewed effort.

Former presidential guard security chief Park Chong-jun, who resigned on Friday and was replaced by a more hardline Yoon loyalist, told reporters there must be no bloodshed during any second arrest attempt.

The National Office of Investigation, a police unit, sent a note to high-ranking police officials in Seoul, requesting that they prepare to mobilize 1,000 investigators for the next attempt, the Yonhap news agency reported.

Protesters for and against Yoon have gathered almost daily in Seoul since the crisis began.

Despite the ongoing crisis, Yoon's ruling party has seen a rise in approval ratings.

A new Gallup survey published on Friday showed the People Power Party's approval rating had increased to 34 percent, up from 24 percent three weeks ago.