South Korean opposition parties introduced a bill Thursday calling for an independent investigation into impeached President Yoon Suk Yeol’s brief martial law declaration, as thousands of his supporters and critics held tense rallies near his residence ahead of his potential detention.

The impeached president faces an attempt by authorities to arrest him over his short-lived Dec. 3 martial law.

It was unclear when and how police could make the arrest and whether the presidential security service, which has blocked access by investigators with a search warrant to Yoon's office and official residence,