His arrest marks a major milestone in prosecutors’ efforts to hold senior officials accountable for what has been described as South Korea’s gravest constitutional crisis since its transition from dictatorship in 1987.

Cho is the third of Yoon’s former cabinet members to be detained, following his defence and home ministers, both of whom were arrested earlier.

Special prosecutors accuse Cho of perjury, dereliction of duty and destruction and falsification of official documents, among other charges. Investigators say he withheld knowledge of Yoon’s December 3 martial law decree and failed to alert parliament even after being warned that troops were preparing to arrest opposition politicians.