The Defense Ministry was on the defensive Monday, forced to explain how a North Korean soldier was able to pass through the heavily armed border undetected earlier this month.

Defense Minister Kim Kwan-jin made a public apology and announced disciplinary measures against those responsible for the incident.

The military has been heavily criticized for failing to detect the North Korean defector on Oct. 2, who climbed through barbed wire and crossed miles of no-man's land before he knocked on the door of an army barracks to say he wanted to defect.

Initially, the military claimed the defector was caught on a surveillance camera and then taken into custody, but an investigation found that he had in fact made his way across the border unnoticed.

Kim said five army generals and nine mid-level officers on the frontline, as well as several officers in the Joint Chiefs of Staff, will be disciplined for trying to cover up the scandal.

Meanwhile, the ministry said security on the inter-Korean border would be strengthened. More surveillance cameras will be installed, and trenches and barbed wire on the border will be fortified.