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.

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.

Finance Minister Choi Sang-mok became on Friday South Korea's second acting president in two weeks, as lawmakers voted to impeach the current acting leader, Prime Minister Han Duck-soo, fuelling political uncertainty in Asia's fourth-largest economy.