Main opposition Democratic Party Chairman Lee Jae-myung has called for the prompt suspension of President Yoon Suk Yeol from his duties as president, saying Yoon is guilty of treason.

The opposition party chair made the call in a special statement on Friday at the National Assembly, saying that South Korea, an advanced democracy, is facing a serious crisis.

Lee accused Yoon of committing treason and abusing the democratic constitutional order for his own personal gain and to strengthen and maintain his power.

Lee said Yoon’s martial law move was an act of treason and a “self-coup,” motivated by the president’s desire to maintain or expand his power.

The opposition party chair also called for a prompt investigation and other necessary steps such as Yoon’s arrest and indictment, saying presidential immunity does not apply to acts of treason.