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.

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.

South Korea's lawmakers on Friday voted to impeach acting President Han Duck-soo, in the second head-of-state ousting this month after a short-lived martial decree on Dec. 3. Han's predecessor, President Yoon Suk Yeol,