South Korea's main opposition party said it will introduce a bill to impeach acting President Han Duck-soo on Thursday and hold a vote on Friday, a move that could deepen the country's constitutional crisis triggered by a short-lived martial law.

The opposition Democratic Party had threatened to impeach Han if he does not immediately appoint three justices to fill the vacancies at the Constitutional Court. Parliament voted in favor of three nominees on Thursday, but they have yet to be formally appointed by Han.

The court is trying the impeachment of President Yoon Suk Yeol over his Dec. 3 declaration of martial law.