North and South Korea exchanged gunfire near one of the South's guard posts inside the demilitarized zone that separates the two countries, the South Korean military said Sunday.

The incident began when North Korean soldiers fired at the guard post several times, South Korea’s Joint Chiefs of Staff said in a statement. The Joint Chiefs said their soldiers fired back twice.

They did not report casualties or damage. A South Korean Defense Ministry official, speaking on the condition of anonymity to discuss sensitive matters, said the guard post was not hit.

Describing a “handful of shots that came across from the North,” U.S. Secretary of State Mike Pompeo said “we think those are accidental.”

“South Koreans did return fire. So far as we can tell, there was no loss of life on either side,” Pompeo said Sunday on ABC’s “This Week.”

The shooting came a day after North Korea broadcast footage of leader Kim Jong Un’s first public appearance in about three weeks. His absence from public eye prompted speculation that he had fallen ill or had died.

On Sunday, an official from South Korea’s presidential Blue House told journalists that the government did not believe Kim had undergone any kind of medical procedure, as had been rumored.

“Our view is that there was no surgery,” the official said. The official said there was evidence to support this view but declined to share it.

Pompeo said “there’s not much that I can share” about what the United States knew about Kim’s activities during his absence. “We know there have been other extended periods of time where Chairman Kim’s been out of public view as well, so it’s not unprecedented.”

But from the images shown on North Korean television, he said, “it looks like Chairman Kim is alive and well.”

Asked whether Kim had ever been gravely ill, and whether he could “rule out” coronavirus infection or a heart problem, Pompeo said: “I just can’t say anything about that.”

The reason North Korea opened fire remains unknown. South Korea’s military said it was contacting its North Korean counterpart via a hotline to figure out what had happened and prevent further escalations. It did not repeat Pompeo’s statement that the exchange was “accidental.”

The demilitarized zone was established as a buffer between the two Koreas as a result of an armistice that halted the Korean War in 1953. Despite its name, the zone contains barbed-wire fences, land mines and combat-ready troops, making it one of the most one of the most heavily guarded frontiers in the world.

The two Koreas began dismantling the front-line guard posts in late 2018 as relations between the countries warmed. But efforts to reduce military tensions have stalled since negotiations to denuclearize North Korea broke down amid disagreements over ending U.S. sanctions aimed at curbing the North’s development of nuclear weapons.

DeYoung reported from Washington.