Seoul, Oct 15 (IANS): South Korea's defence minister Monday publicly apologized over the security lapse at the heavily fortified border following revelations that a

North Korean defector crossed over undetected.

Contrary to the military's initial account of the incident, inspectors later found out that the 22-year-old North Korean soldier, who said he killed his superior before

crossing the Military Demarcation Line Oct 2, was not spotted until he knocked on the door of a barrack and surrendered, reported Xinhua.

The security vacuum and the attempted cover-up drew harsh criticism from the public wary of lingering cross-border tensions after two deadly border incidents in

2010 killed 50 South Koreans.

"I sincerely apologize for causing public concern," Defence Minister Kim Kwan-jin said at a press conference in Seoul, acknowledging a "surveillance failure".

A total of 14 high-ranking military officials, including five generals, will face disciplinary measures, the minister said, pledging to beef up security along the border and

reinforce border fences "as soon as possible".

The two Koreas remain technically at war with each other after the 1950-53 Korean War ended with a truce instead of a peace treaty.

Some 24,000 people have fled North Korea and defected to the South since the division of the Korean peninsula, according to government data.