Both Koreas breached their armistice agreement when they exchanged gunfire at the border on May 3, the United National Command said Tuesday, after a weeklong investigation by its multinational team.

The UN Command, which administers the Demilitarized Zone separating both Koreas and enforces the armistice that halted the 1950-53 Korean War, said it could not definitively determine whether North Korea opened fire on a South Korean guard post intentionally or by mistake.

Seoul expressed regret over the finding, saying its troops had retaliated in accordance with the contingency manual. “We reaffirm that our response to the North’s firings were without any fault and in accordance with our guidelines drawn out for such incidents,” the Defense Ministry said.

On May 3, North Korea fired four shots from small firearms toward a South Korean guard post inside the DMZ. South Korean troops returned fire with two shots. The Defense Ministry said the North opened fire by mistake, though many experts here disputed the assessment.

The gunfire exchange, which highlighted the latest confrontation between the two Koreas amid frosty inter-Korean relations, sparked speculation over Pyongyang’s intentions because it came two days after its leader Kim Jong-un resurfaced in public. Kim had not made public appearances for almost three weeks.

The UNC said it had received full cooperation from Seoul while none came from Pyongyang while running the investigation. The UNC said it will engage both Koreas to prevent a recurrence.

By Choi Si-young (siyoungchoi@heraldcorp.com)