South Korean Defense Minister Song Young-moo has ordered the military to take measures to fend off North Korea's hacking attempts, his ministry said Thursday.

The move came amid public criticism of the defense authorities over a fresh allegation that the North's hackers stole a vast cache of classified military documents in 2016.

The leaked data includes a South Korea-US wartime operational plan and a "decapitation" scheme to remove the Kim Jong-un leadership in the communist nation, according to Rep. Lee Cheol-hee of the ruling Democratic Party.

There have been a number of reports on the North's cyber threats, including its hacking into the South's military database, which was made public in September last year. But the scale of the hacking had remained undisclosed.

Song and other ministry officials neither confirmed nor denied Lee's claim.

The minister pointed out the cited hacking case occurred under the previous administration of Park Geun-hye.

"Nonetheless, related measures that have been taken stop short of the people's expectations," he said.

He instructed the military to closely review what has been done and find ways to beef up cybersecurity. (Yonhap)