South Korea’s conservative President Yoon Suk Yeol has reportedly failed to comply with a summons from prosecutors investigating him for insurrection, among other things, as he faces impeachment proceedings following the declaration of martial law.

According to Yonhap News Agency, Yoon, who was sent a summons on Wednesday asking him to appear for questioning at 10 a.m. local time on Sunday, did not appear. Yoon and other senior officials are being investigated over possible allegations of insurrection, abuse of office and obstruction of the exercise of their rights.

Yonhap said prosecutors – who are also seeking arrest warrants for senior military officials, including the head of the Army’s Special Warfare Command and the head of the Capital Defense Command – plan to issue another subpoena for the president.

The president’s reported no-show came a day after South Korean lawmakers voted to impeach him over the unsuccessful attempt to declare martial law nearly two weeks ago, plunging the country into some of its worst political turmoil in decades.

In a late-night televised address to the nation on Dec. 3, Yoon announced he would impose martial law and accused the opposition of trying to paralyze the government through “anti-state activities.”

The declaration of martial law – the first of its kind in more than four decades – lasted just six hours, and hundreds of Yoon troops and police sent to the National Assembly withdrew after the presidential decree was repealed. There was no major violence.

Yoon’s powers have been suspended until the Constitutional Court decides whether to remove him from office or reinstate him. If Yoon is fired, a nationwide election to choose his successor must be held within 60 days.

The court will convene Monday to begin considering the case and has up to 180 days to make a decision. But observers assume that a verdict could come more quickly. In the case of the parliamentary impeachment of former presidents Roh Moo-hyun in 2004 and Park Geun-hye in 2016, the court spent 63 and 91 days, respectively, before deciding to reinstate Roh and dismiss Park.

South Korea’s main opposition leader, Lee Jae-myung, has offered to work with the government to ease political turmoil as officials seek to reassure allies and markets following the impeachment vote.

Lee, who leads the Democratic Party and has spearheaded the political offensive against Yoon’s embattled government, is considered the leading candidate to succeed him. Lee has called on the Constitutional Court to quickly decide on Yoon’s removal from office and proposed a special council for cooperation between the government and parliament.

The opposition leader told a televised news conference that a quick decision was the only way to “minimize national confusion and people’s suffering.”

Lee also proposed a National Council in which the government and the National Assembly would work together to stabilize state affairs and said his party would not seek to impeach Prime Minister Han Duck-soo, a candidate appointed by Yoon to serve as acting president functions.

“The Democratic Party will actively work with all parties to stabilize state affairs and restore international trust,” Lee said. “The National Assembly and the government will work together to quickly resolve the crisis that has gripped the Republic of Korea.”

As Han assumed his role as acting leader, he ordered the military to strengthen its security posture against North Korea. He called on the foreign minister to inform other countries that South Korea’s key foreign policies would remain unchanged and called on the finance minister to work to minimize possible negative effects of the political unrest on the economy.

On Sunday, Han held a phone call with U.S. President Joe Biden in which they discussed the political situation in South Korea and regional security challenges, including the North’s nuclear program. Biden expressed appreciation for the resilience of democracy in South Korea and reaffirmed the U.S.’s “iron-clad commitment,” according to both governments.

Opposition parties accused Yoon of rebellion, saying a president in South Korea can only declare martial law in times of war or similar emergencies and even in those cases has no right to suspend the work of parliament.

Yoon has denied the allegations and vowed to “fight until the end.” He said the deployment of troops in the National Assembly was intended to sound a warning to the Democratic Party, which he described as an “anti-state force” that was abusing its control over parliament by stalling the government’s budget proposal for next year and repeatedly pressured top officials to indict.

Law enforcement agencies are investigating possible rebellion and other allegations. They arrested Yoon’s defense minister and police chief, as well as two other high-ranking figures.

As president, Yoon enjoys immunity from most criminal prosecutions, but this does not apply to charges of rebellion or treason. He has been banned from leaving South Korea, but observers doubt authorities will detain him because of possible clashes with the presidential security detail.

With Agence France-Presse, Reuters and Associated Press