President Moon Jae-in on Friday called for swift measures to overhaul the military intelligence unit, saying its controversial proposal in late 2016 to invoke martial law against anti-government protests represented an illegal act.

"The military must fear the people more than anyone else. The Defense Security Command's (DSC) inspection of the families of people killed in the Sewol ferry sinking and its proposal to consider martial law are illegal acts that should not have taken place in the first place," the president said while meeting with the country's top military commanders at his office Cheong Wa Dae.

"The DSC must become a unit that contributes to the strengthening of our defense capabilities by strictly adhering to its natural mission," the president added, while urging efforts to quickly reform the military intelligence unit. Moon's remarks follow a recent controversy over the 2016 proposal from the DSC to invoke martial law during the months of protests against then-President Park Geun-hye.

Related documents disclosed earlier by Cheong Wa Dae showed that the DSC had even proposed taking control of the parliament by arresting then-opposition lawmakers, prompting suspicions over a possible coup attempt.

Friday's meeting also comes amid a dispute between Defense Minister Song Young-moo and the DSC, which claims the defense chief had determined its martial law proposal was within its legal boundaries, leading to its failure to submit or disclose related documents.

Song has flatly denied the claim, only stopping short of accusing the DSC of a mutiny.

In his latest instruction regarding the martial law proposal, President Moon on Thursday said anyone responsible for any wrongdoing or mistakes will be asked to answer. He earlier ordered the launch of an independent investigation into the martial law proposal. He has also ordered the military and the defense ministry to submit all their related documents.

Still, the president said finding who is at fault could wait.

"The key issue is to reveal the truth about the martial law documents. We must thoroughly identify why (the military) created such documents and how far it was willing to execute the plan," Moon said, according to Cheong Wa Dae spokesman Kim Eui-kyeom.

He also stressed the need to reform the DSC, the most powerful military intelligence unit.

"The need to reform the DSC has become greater," the Cheong Wa Dae spokesman quoted Moon as saying. "I ask the task force on the DSC reform to speed up its discussions and submit a reform proposal at an early date." (Yonhap)