North Korea fired two shots at a guard post stationed in Cheolwon, Gangwon Province in South Korea at 5:26 p.m. Friday Korea time.
Seoul's Joint Chiefs of Staff said the bottom of the South Korean guard post was hit by North Korean machine gun fire but no damage or injuries were reported.
The South Korean military immediately fired back three shots and sent a warning message to the North saying that it is breaching the ceasefire agreement.
The military official said no further movement from the communist state was detected following the initial shots and that it is uncertain whether the shots were intentional or were fired by mistake.
After the shots by the North were reported the United Nations Command said it intends to send a team in the near future to further investigate the incident.