SEOUL - South Korean prosecutors Sunday booked President Yoon Suk-yeol as a suspect on charges of treason, Yonhap news agency reported.

Park Se-hyun, who leads a special investigation headquarters into Yoon's short-lived martial law declaration, said the prosecution is investigating charges of treason and abuse of power against the president, according to the report.

"Numerous complaints have been submitted, and an investigation is underway in accordance with the process," Park said.

While the president mostly has immunity from prosecution while in office, that does not extend to allegations of rebellion or treason.

Earlier in the day, prosecutors arrested former Defense Minister Kim Yong-hyun, who allegedly recommended Tuesday's brief martial law imposition to Yoon, making him the first figure detained over the case.

The main opposition Democratic Party of Korea Sunday called for the immediate arrest and investigation of Yoon over his martial law decree.