South Korea’s impeached President Yoon Suk-yeol has been charged with insurrection after he tried to declare martial law in December.

His ill-fated attempt to impose military rule plunged the country into an unprecedented political crisis and he becomes the first president in South Korean history to be charged with a crime.

The indictment was issued after a Seoul court rejected a request on Saturday to extend Yoon’s detention, meaning prosecutors had until Monday to decide whether to charge or release him.

“The punishment of the leader who led the rebellion has finally begun,” Han Min-soo, a spokesman for the main opposition Democratic Party, said at a press conference.

Yoon’s legal team criticized the indictment and vowed to expose “illegal acts in the investigation.”

“The indictment has made a serious mistake, and the indictment division of the CIO has been turned into a tool for political interests,” Yoon’s lawyers said, referring to the Central Bureau of Investigation for high-ranking officials.

In South Korea, rebellion carries a sentence of life imprisonment or the death penalty. However, the latter is unlikely, as the country has not carried out the death penalty for decades.

Separately, the Constitutional Court has begun deliberations on whether to formally remove Yoon from office or reinstate him.

The impeached president has largely refused to cooperate with the criminal investigation into the martial law declaration.

Yoon is set to stand trial alongside his former defense minister and senior military commanders, who are accused of helping him plan and execute the takeover attempt.

In an unprecedented televised address on December 3, Yoon said he was declaring martial law to protect the country from “anti-state” forces sympathetic to North Korea.

At the time, the embattled leader was embroiled in a budget impasse, with corruption scandals and several of his cabinet ministers under investigation.

The military announced it would suspend all parliamentary proceedings and sought to impose controls on media outlets.

Opposition Democratic Party leader Lee Jae-myung called on the public to protest in the National Assembly and urged his fellow lawmakers to vote immediately to repeal the order.

Less than two hours after Yoon’s statement, 190 lawmakers, including some from the president’s party, voted unanimously to block it.

In a dramatic clash, soldiers armed with rifles were seen entering the parliament building through broken windows.

Thousands of civilians gathered in front of the chamber to try to block the soldiers.

On December 14, the parliament impeached Yoon and suspended him from his duties.

The incident has triggered South Korea’s worst political crisis in decades and has polarized the country.

Many of his hardline supporters have rallied around him. On Friday, tens of thousands of people gathered to protest, demanding his release and reinstatement.

If Yoon is removed from office, a presidential election would be held within 60 days.