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

Tens of thousands of North Koreans have fled to South Korea since the peninsula was divided by war in the 1950s, but defections across the land border are relatively rare.

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