Former South Korean Defense Minister Kim Yong-hyun, who last week claimed responsibility for the president's failed attempt to place the country under martial law, attempted suicide, an official said.
Authorities found him making the attempt at his detention center Tuesday evening, Shin Yong-hae, head of the Justice Ministry's corrections agency, told lawmakers.
Following Yoon's shock martial law order, Kim resigned last week, along with other senior presidential officials.
He was arrested on Sunday for investigation, before being officially arrested for insurrection.
Kim was in stable condition after the attempt, Shin said.
Kim is among senior officials being investigated for their role in Yoon's short-lived martial law order, which sparked widespread fury in South Korea.
Tens of thousands of people took to the streets to demand the resignation or impeachment of the president.
Yoon is also under investigation for alleged insurrection. Although he apologized for the declaration of martial law, he did not accept growing calls for his resignation.
