South Korean President Yoon Seok-yeol was charged with rebellion after trying to declare martial law in December.

His failed attempt to impose military rule plunged the country into an unprecedented political crisis, and he became the first sitting president in South Korea's history to be charged with a crime.

A Seoul court on Saturday rejected a request to extend Yoon's detention, meaning prosecutors have until Monday to decide whether to charge or release him.

"The punishment of the rebel leaders has now finally begun," Han Min-soo, spokesman for the main opposition Democratic Party, told a news conference.

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

Impeached president largely refuses to cooperate with administration criminal investigation Regarding the declaration of martial law.

Yin will stand trial along with his former defense minister and top military commanders, who are accused of helping him plan and carry out his attempt to seize total power.

In an unprecedented televised statement on December 3, Yoon said he would invoke martial law to protect the country from "anti-national" forces sympathetic to North Korea.

At the time, the embattled leader was deadlocked over a budget bill and dogged by a corruption scandal, with several of his cabinet ministers under investigation.

The military announced the suspension of all parliamentary activities and attempted to control the media.

Lee Jae-myung, leader of the opposition Democratic Party, urged people to protest at Congress and asked lawmakers to vote to repeal the order immediately.

Less than two hours after Yoon's statement, the 190 lawmakers gathered, including some from the president's own party, voted unanimously against it.

Soldiers armed with rifles were seen entering the parliament building through broken windows and dramatic clashes ensued.

Thousands of civilians gathered in front of the rally to try to hold back the soldiers.

Yin was impeached by parliament on December 14 and suspended from office.

The incident sparked South Korea's worst political crisis in decades and polarized the country.

Many of his hardline supporters rallied around him. Tens of thousands of people gathered in protests on Friday, demanding his release and return to office.

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

The prosecutor's office did not immediately respond to a request for comment.