South Korea's main opposition party introduced a bill to impeach acting President Han Duck-soo on Thursday, a day before it plans to seek a vote on the move, which could deepen a constitutional crisis triggered by a short-lived martial law.

South Korean investigators on Friday pressed ahead with their probe into impeached President Yoon Suk Yeol over his Dec. 3 martial law declaration, issuing another summons demanding that he appear for questioning on Christmas Day,

South Korea’s parliament voted to impeach President Yoon Suk Yeol on Saturday in an extraordinary rebuke that came about after his own ruling party turned on him following his refusal to resign over his short-lived martial law attempt.