Former South Korean President Yoon Suk-yeol is being held in solitary confinement under conditions that have prompted concern from his legal adviser.

South Korea’s jailed ex-President Yoon Suk Yeol again refused to attend questioning by investigators Friday, using a new method to resist: He took off his prison uniform and lay down on the floor at his detention room.

South Korea’s impeached former President Yoon Suk Yeol lay on his prison cell floor in his underwear to resist attempts to interrogate him, prosecutors say. Prosecutors obtained a fresh arrest warrant on Thursday to forcibly bring the former leader in for questioning over allegations of election tampering.