President Yoon Suk Yeol, right, and former Defense Minister Kim Yong-hyun are seen in this Oct. 1 photo. Newsis

Prosecutors have seized former Defense Minister Kim Yong-hyun's mobile phone to try to access phone calls he held during President Yoon Suk Yeol's brief imposition of martial law, legal sources said Saturday.

Kim was indicted Friday on charges of playing a key role in an insurrection amid allegations he proposed declaring martial law to Yoon and ordered military officials to send troops to seal off the National Assembly, Dec. 3.

The prosecution's special investigation headquarters handling the martial law case seized the phone on Thursday with a court-issued warrant and notified Kim's side to attend a forensic survey of the phone scheduled for next Monday, according to the sources.

Prosecutors earlier secured the phone when Kim voluntarily appeared for questioning, Dec. 8, but Kim's side protested against what they said was the illegal collection of evidence.

Instead of returning the phone, prosecutors filed for a warrant and succeeded in securing the phone again.

Kim's lawyer, however, submitted an appeal with a court Friday to overturn the seizure. (Yonhap)