A man observed crossing the heavily fortified border from South Korea into North Korea last week is believed to be a North Korean who previously defected to the South in 2020 in the same area, Seoul's defence ministry said on Monday.

South Korea's Joint Chiefs of Staff (JCS) had said it carried out a search operation after detecting the person on Saturday on the eastern side of the Demilitarised Zone (DMZ) separating the two Koreas.