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 voted Friday to impeach acting President Han Duck-soo despite vehement protests by governing party lawmakers, further deepening the country’s political crisis set off by President Yoon Suk Yeol’s stunning imposition of martial law and ensuing impeachment.

The vote intensifies a political crisis as the Constitutional Court meets for its first hearing on suspended President Yoon Suk Yeol's short-lived martial law.