Former Defense Minister Kim Yong-hyun looks through the filed document during a meeting at the National Assembly in Yeongdeungpo District, Seoul, Nov. 15. Yonhap

The detention period of former Defense Minister Kim Yong-hyun has been extended until Dec. 28, the prosecution said Tuesday, as he has refused to cooperate in the investigation into President Yoon Suk Yeol's Dec. 3 martial law declaration.

Kim was put under emergency arrest on Dec. 8 as a key suspect in the martial law-related probe and his legal detention period was set to end 10 days later on Tuesday. The prosecution applied for the extension of his detention period earlier this week and the court approved the request earlier Tuesday.

Under the Criminal Procedure Act, a prosecutor can extend a suspect's detention period once, not exceeding 10 days, with the permission of the court.

The prosecution appears to have extended Kim's detention, as he has refused to testify and the investigation of key figures involved in his case is still ongoing. (Yonhap)