A soldier from North Korea managed to make a rare successful escape across the heavily fortified border with South Korea, on the same day a US national was detained as he attempted to enter the North.

The North Korean guard stationed within the Joint Security Area fled across the border into the South early on Monday, sustaining gunshot wounds to his shoulder and elbow after being fired on by other North Korean guards.

The soldier was airlifted by a United Nations Command helicopter to a hospital for treatment, military officials told Yonhap, and his injuries are not believed to be life-threatening.

Cases of North Koreans successfully crossing the Demilitarised Zone into the South are rare because of the landmines, tripwires and machine guns that are trained across the border.

Defections within the JSA are even less common, because the North Korean troops assigned to the small area where the two sides' militaries are face to face are hand-picked for their loyalty to the regime.