A North Korean soldier was taken into custody by the South after he voluntarily crossed the heavily fortified land border separating the two Koreas on Sunday, Seoul's military said.

The soldier was seeking to "to defect to the South", a defense ministry official said.

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 the South.