A North Korean civilian voluntarily crossed the heavily mined land border separating the Koreas, aided by the South's military in a delicate 20-hour operation, Seoul's Joint Chiefs of Staff (JCS) said Friday.

Tens of thousands of North Koreans have fled to South Korea since the peninsula was divided by war in the 1950s, with most going overland to neighboring China first, then entering a third country such as Thailand before finally making it to South Korea.

Defections across the land border that divides the peninsula are relatively rare, as the area is densely forested, heavily mined and monitored by soldiers on both sides.