South Korea’s defense chief offered a public apology after a North Korean defector walked in across the border undetected, drawing skepticism on the strength military’s security measures.

Defense Minister Kim Kwan-jin said he “deeply” apologizes for the anxiety caused by the security breach. “There were (sic) an obvious failure in security operations and faults in situation-reporting systems,” Kim told a news conference.

Asahi Shimbun reports that President Lee Myung-bak ordered tough punishment for those found responsible. Ministry spokesman Kim Min-seok said that 14 officers, including 5 high-ranking officials, are under investigations, adding that the ministry has already dismissed 3 officers.

A statement from the ministry said that border security will be strengthened with more guards, modern surveillance equipment and more wire fences to avoid another “walk in.”

According to AP, the soldier scaled the North’s electric fences and barbed wire fences in the South, all the while undetected. South Korean soldiers were only aware of his presence when he knocked on their barracks late at night.