South Korea’s Constitutional Court will begin on Monday reviewing the impeachment of President Yoon Suk Yeol over his Dec. 3 martial law attempt, while investigators said they plan to question him this week.

All six current justices of the court will attend the first meeting over the impeachment, which the opposition-led parliament passed on Saturday. The court has up to six months to decide whether to remove Yoon from office or to reinstate him.

Justice Kim Hyung-du said the Constitutional Court will discuss procedures and how to conduct arguments.

In 2017, the court began oral arguments about three weeks after parliament voted to impeach then-President Park Geun-hye over abusing the powers of her office, and took three months to issue a ruling to strip her presidency.

Yoon and a number of senior officials face potential charges of insurrection, for the short-lived martial law.

A joint team of investigators from the police, the defence ministry and an anti-corruption agency are planning to call Yoon in for questioning at 10 a.m. (0100 GMT) on Wednesday, a police official told Reuters.

On Sunday Yoon did not appear in response to a summons for questioning by a separate investigation by the prosecutors’ office, Yonhap news reported. Yoon cited he was still forming a legal team for his defence as the reason, it said.

The government led by acting president, Han Duck-soo, was moving quickly to reassure international partners and calm financial markets, while the main opposition party pledged to cooperate in efforts to stabilise the situation.

Early on Monday, the finance minister, Bank of Korea governor and top financial regulators met and pledged around-the-clock monitoring of financial and foreign exchange markets.

The benchmark KOSPI index (.KS11), opens new tab rose for a fifth straight session on Monday and traded at its highest levels in more than two weeks, as authorities vowed to stabilise financial markets and analysts noted eased political uncertainty.

Yoon’s surprise martial law declaration and the ensuing political crisis spooked markets and South Korea’s diplomatic partners, worried over the country’s ability to deter nuclear-armed North Korea.

In one of his first moves as acting president, Han spoke with US President Joe Biden by telephone on Sunday, pledging unwavering commitment to pursue foreign and security policies based on the alliance between the two countries.

Opposition Democratic Party leader Lee Jae-myung welcomed US President-elect Donald Trump’s selection of his former intelligence chief to handle special missions including North Korea as a sign of commitment for dialogue to ease tensions.

The Saturday impeachment vote passed with at least 12 members of Yoon’s ruling People Power Party joining in favour, which has thrown the party into a disarray with its leader Han Dong-hoon announcing his resignation on Monday.

Han had publicly backed Yoon’s impeachment as the only way to restore order in the country and clashed with some members who continued to oppose the move.