Border guards from the two Koreas have briefly traded fire along the demilitarized zone with no casualties or injuries reported on the South’s side.

According to the South’s Joint Chiefs of Staff Tuesday, North Korean soldiers fired two shots towards a South Korean guard post around 7:30 Monday morning in Yanggu, located in the eastern part of the demilitarized zone (DMZ).

South Korean soldiers immediately fired six bullets back in line with the rules of engagement.

One of the two North Korean bullets hit the wall of the boiler room of the South Korean guard post while the other bullet trailed off nearby.

An official of the Joint Chiefs of Staff stressed the need for a thorough investigation into the shootout to confirm whether it had been an accident.

Meanwhile, the South’s military has stepped up guard along the border in the wake of Monday’s incident.