SEOUL, South Korea — Police are considering placing an overseas travel ban on South Korean President Yoon Suk Yeol as they investigate possible rebellion charges over his brief imposition of martial law last week, reports said Monday.

Yoon’s martial law decree last Tuesday, which brought armed special forces troops into Seoul streets, is plunging South Korea into huge political turmoil. On Sunday, he avoided an opposition-led bid to impeach him, with most ruling party lawmakers boycotting a floor vote. But the opposition parties vowed to submit a new impeachment motion against him this week.

On Monday, Yonhap news agency cited police as saying that they are considering banning Yoon from leaving the country as they investigate charges of rebellion. Other South Korean media carried similar reports.

Repeated calls to the National Police Agency weren’t immediately answered.

The main opposition Democratic Party called Yoon’s martial law imposition “unconstitutional, illegal rebellion or a coup.” It has filed complaints with police against at least nine people, including Yoon and the former defense minister, over the alleged rebellion.

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

South Korean prosecutors on Sunday detained former Defense Minister Kim Yong Hyun, who allegedly recommended Yoon declare martial law. He became the first person detained over the martial law case.

The Defense Ministry said it has separately suspended three top military commanders over their alleged involvement in imposing martial law. They were among those facing the opposition-raised rebellion allegations.

On Saturday, Yoon issued an apology over the martial law decree, saying he won’t shirk legal or political responsibility for the declaration. He said he would leave it to his party to chart a course through the country’s political turmoil, “including matters related to my term in office.”

Since taking office in 2022 for a single five-year term, Yoon has struggled to push his agenda through an opposition-controlled parliament and grappled with low approval ratings amid scandals involving himself and his wife. In his martial law announcement on Tuesday night, Yoon called parliament a “den of criminals” bogging down state affairs and vowed to eliminate “shameless North Korea followers and anti-state forces.”