A North Korean soldier has defected to the South through the heavily-militarised border, telling Seoul military personnel that he had shot dead two officers.
The soldier said he shot dead his platoon leader and a company commander before crossing the border, South Korean military officials said.
The Joint Chiefs of Staff said South Korean border guards heard shots across the border before the defecting soldier appeared.
The soldier is in protective custody being questioned by intelligence agents.
Defections across the tightly-guarded and heavily-armed De-militarised Zone are rare.
The two Koreas have not signed a peace treaty since the 1950-53 war.