South Korea's acting president faces an impeachment vote on Friday, intensifying a political crisis as the Constitutional Court meets for its first hearing on suspended President Yoon Suk Yeol's short-lived martial law declared on Dec. 3.

The push to impeach Prime Minister Han Duck-soo, who has been acting president since Yoon was impeached on Dec. 14, has thrown South Korea's once-vibrant democratic success story into uncharted territory and watched with concern by allies.

Opposition leader Lee Jae-myung said his Democratic Party, which has majority control of parliament, will go ahead with the plan to impeach the acting president, accusing Han of "acting for insurrection."