Yeo In-hyung, former chief of Defense Counterintelligence Command, attends a parliamentary hearing held at the National Assembly in Yeouido, Seoul, Saturday. (Yonhap)

The prosecution's special investigation team on Saturday arrested three-star Army Gen. Yeo In-hyung, the former chief of the Defense Counterintelligence Command, over his alleged involvement in impeached President Yoon Suk Yeol's Dec. 3 martial law declaration.

Yeo is accused of playing a key role in the martial law plan, including participating in discussions to plan the declaration. His charges include deploying DCC personnel to the National Assembly in Yeouido, Seoul and the National Election Committee’s headquarters in Gwacheon, Gyeonggi Province; and contacting the heads of the National Intelligence Service and the National Police Agency to provide lists of individuals to be apprehended.

The military court approved the arrest warrant sought by the prosecution Saturday evening, reportedly saying Yeo's charges were considered grave enough to prevent a flight risk.

While Yeo had previously denied the allegations, he has stated his intention to cooperate with investigations.

Yeo is the second military figure to be detained in connection with the martial law case, following former Defense Minister Kim Yong-hyun, who allegedly proposed the declaration to Yoon. He is also the first sitting military man arrested in relation to the martial law probe.