Police summoned former Interior Minister Lee Sang-min on Monday as a suspect in connection with President Yoon Suk Yeol's martial law declaration, where he faces allegations of insurrection.

The special investigation team for police said Lee and his lawyers arrived at the National Office of Investigation for investigation into his role in Yoon's botched martial law declaration at 2 p.m. Monday.

Lee, a close confidant to Yoon, is accused of conspiring with the president to plan and endorse the Dec. 3 martial law declaration, and now faces charges of insurrection. He attended a Cabinet meeting held just prior to Yoon’s unexpected declaration.

A junior alumnus of Yoon, Lee attended Choongam High School and majored in law at Seoul National University alongside the suspended president.

Lee was placed under a travel ban by the Justice Ministry on Dec. 8.

Last week, Lee announced his resignation a day after the opposition bloc submitted an impeachment bill, as he claimed full responsibility for failing to effectively serve the public and for inadequately advising the president.