“It has been confirmed that the person crossed the military demarcation line to the north,” the statement added.
The person has not yet been identified, a committee official said, adding that South Korean authorities had sent a message to the North regarding the incident.
The army launched a search but to no avail.
Due to years of repression and poverty, more than 30,000 people fled from North Korea to South Korea in the decades after the Korean War (1950-1953), but crossings in the other direction are extremely rare.
The vast majority of North Koreans who decide to flee usually first flee to China and from there to South Korea.
Only a few dared to cross the “demilitarized zone” surrounded by barbed wire in which a large number of mines were placed.