South Korean prosecutors formally indicted President Yoon Suk Yeol on Sunday, charging him with insurrection over his controversial declaration of martial law in December, according to opposition lawmakers and local media reports.

Democratic Party spokesman Han Min-soo announced the development during a press conference. “The prosecution has decided to indict Yoon Suk Yeol, who is facing charges of being a ringleader of insurrection,” Han stated, as reported by Reuters. “The punishment of the ringleader of insurrection now begins.”

Yoon declared martial law on December 3 in a televised address, asserting that the move was necessary to counter the actions of the Democratic Party. He accused the opposition of controlling parliament, sympathizing with North Korea, and rendering the government dysfunctional.

The indictment follows a dramatic turn of events in late December when a South Korean court issued an arrest and search warrant for Yoon. After a prolonged stand-off with his presidential security detail, prosecutors apprehended him at his residence ten days ago.

Yoon, who was suspended from his position on December 14, has vowed to contest the charges. His declaration of martial law and the subsequent legal actions have plunged South Korea into political turmoil, with the indictment marking an unprecedented moment in the nation’s democratic history.