Seoul: 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. The move 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 did not immediately appoint three justices to fill the vacancies at the Constitutional Court. Parliament voted in favour 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 December 3 declaration of martial law. "It has become clear that Prime Minister and acting President Han Duck-soo does not have the qualification or the will to safeguard the Constitution," Democratic Party floor leader Park Chan-dae said in a statement.

The motion was introduced to parliament on Thursday and must be voted on within 24-72 hours. It cited a range of actions by Han as grounds for his impeachment, including his veto of a special prosecutor bill to investigate alleged wrongdoings by the first lady. If Han is impeached, the finance minister will assume the role of the acting president.