South Korean investigators are seeking an arrest warrant for impeached President Yoon Suk Yeol, marking the first time a sitting president has faced such legal action in the country’s history, media reports said early Monday.

A joint investigation team comprising the Corruption Investigation Office for High-ranking Officials (CIO), police and the Defense Ministry’s investigation unit announced that it sought the warrant on charges of insurrection and abuse of power, according to Yonhap News Agency.

The request was filed at midnight Sunday with the Seoul Western District Court, the report noted.

The charges stem from Yoon’s declaration of martial law on Dec. 3, during which he allegedly ordered troops to the National Assembly to prevent lawmakers from overturning the decree.

Investigators allege that Yoon’s actions amounted to leading an insurrection and abusing his executive authority.

Yoon has denied the accusations, calling the martial law declaration an "act of governance" meant to caution the opposition party against what he described as an abuse of legislative power.

Yun Gap-geun, one of Yoon's legal representatives, criticized the CIO’s involvement.

"It's a request by an agency that does not have the authority to investigate (insurrection charges)," he said.

He further vowed to take "formal steps" in response.

The unprecedented case has sparked widespread debate about the limits of presidential power and accountability in South Korea.