The soldier crossed into Goseong county on the east coast which borders North Korea and was taken into custody by South Korean guards who had been monitoring his movements, the news agency said.

A South Korean defence ministry official said the military took into custody a person who is believed to be North Korean on the eastern front and authorities were questioning the motives for the crossing. The official declined to provide further details.

Yonhap reported the North Korean soldier was a staff sergeant.

A North Korean resident defected to the South earlier this month at the west coast. Defections by North Koreans across the border are considered risky and relatively rare and most escapees make their way to the South through China or other third countries.