SEOUL—South Korea’s legislature voted to impeach acting President Han Duck-soo on Friday after he declined to make judicial appointments needed to advance the impeachment of his predecessor, extending the political upheaval that began with a short-lived martial law declaration earlier this month.

South Korea’s opposition-controlled National Assembly has voted to impeach the country’s acting leader, Han Duck-soo.

As the president awaits an impeachment trial, the country’s interim leader may, too, be ousted. The currency has plunged as the crisis has deepened.