President Moon Jae-in on Wednesday rebuked the military for failing to detect a man who crossed the eastern inter-Korean border into North Korea over the weekend, calling for the military to have a special sense of alert in border security.

The man, who was found to be a North Korean defector, crossed the heavily fortified border on Saturday despite surveillance cameras having caught him as many as five times in a major security failure, according to the military.

Moon said the "failure of security operations" at the eastern border is a "grave problem that should not have happened," according to presidential spokesperson Park Kyung-mee.

"With regard to the issue that such situation was repeated, the military should have a special sense of alert and responsibility," Park quoted Moon as saying.

Moon also ordered the military to conduct a special inspection in front-line units to prevent such incident from happening again, Park said.

Accordging to the military, the defector climed over the barbed wire fence to enter the Demilitarized Zone separating the two Koreas and then raced across the Military Demarcation Line despite eleventh-hour efforts to stop him.

After defecting to the South, the man is known to have worked as a cleaner here, an indication that he might have had economic difficulties. Other details about him were not immediately known.

The latest incident came in spite of the South Korean military's pledge to overhaul its border defense system with stronger surveillance equipment to forestall any security lapses in the wake of earlier border breaches. (Yonhap)