A North Korean soldier defected to the South across the heavily militarized border separating the two on Tuesday, South Korea's Yonhap news agency reported, citing a government source.
The soldier crossed into the eastern province of Gangwon on Tuesday evening and expressed a wish to defect, the unidentified source said.
The circumstances of the reported defection were being investigated.
North Korean soldiers have periodically defected to the South in recent years. Numerous civilians have also defected, usually via a more circuitous route through China.