South Korean prosecutors indicted impeached President Yoon Suk Yeol Sunday for being the "ringleader of an insurrection" after his abortive declaration of martial law, ordering the suspended leader to remain in detention.
Yoon plunged the country into political chaos with his December 3 bid to suspend civilian rule, a move which lasted just six hours before lawmakers defied armed soliders in parliament to vote it down.
He was impeached soon after, and earlier this month became the first sitting South Korean head of state to be arrested.
That came after a weeks-long hold out at his residence where his elite personal security detail resisted attempts to detain him.
In a statement, prosecutors said they had "indicted Yoon Suk Yeol with detention today on charges of being the ringleader of an insurrection".
He has been held at the Seoul Detention Center since his arrest, and the formal indictment with detention means he will now be kept behind bars until his trial, which must happen within six months.
The indictment was widely expected after a court twice rejected requests by prosecutors to extend his arrest warrant while their investigation proceeded.
"After a comprehensive review of evidence obtained during investigations (prosecutors) concluded that it was only appropriate to indict the defendant," they said in a statement.
The need to keep Yoon behind bars was justified by a "continued risk of evidence destruction", they said.
The specific charge -- being the ringleader of an insurrection -- is not covered by presidential immunity, they added.
The opposition hailed the indictment.
"We need to hold not only those who schemed to carry out an illegal insurrection, but also those who instigated it by spreading misinformation," said lawmaker Han Min-soo.
Without providing evidence, Yoon and his legal team have pointed to purported election fraud and legislative gridlock at the opposition-controlled parliament as justification for his declaration of martial law.
Yoon has vowed to "fight to the end", earning the support of supporters who have adopted the "stop the steal" rhetoric associated with US President Donald Trump.
"This indictment will provide a sense of relief, reaffirming that the constitutional order is functioning as it should," said Bae Kang-hoon, co-founder of political think tank Valid.
Yoon also faces a series of Constitutional Court hearings, to decide whether to uphold his impeachment and strip him formally of the presidency.
If the court rules against Yoon, he will lose the presidency and an election will be called within 60 days.
