North Korean troops have opened fire across the demilitarised zone dividing the peninsula, prompting South Korean forces to fire back. The rare exchange of gunfire took place on Sunday, a day after North Korean state media reported the country's leader Kim Jong-un made his first public appearance in about three weeks. Mr Kim's absence caused intense speculation about his health and fears about the stability of North Korea. A South Korean guard post was hit by several shots fired from the North Korea, the joint chiefs of staff in Seoul said. No casualties were reported in the South, they said. "Our military responded with two rounds of gunfire and a warning announcement," the joint chiefs said. The South Korean military said the North Korean gunshots were "not deemed intentional", according to Seoul's Yonhap News Agency. The nations remain technically at war after the Korean War ended with an armistice in 1953. Despite its name, the demilitarised zone is one of the most fortified places on Earth, replete with minefields and barbed-wire fences. Easing military tension on their border was one of the agreements reached between Mr Kim and South Korean President Moon Jae-in at a summit in Pyongyang in September, 2018. Choi Kang, vice president of the Asian Institute for Policy Studies in Seoul, said the timing of the "grey area" provocation showed Mr Kim was still in charge of the North Korean military. "Yesterday, Kim was trying to show he is perfectly healthy, and today, Kim is trying to mute all kinds of speculation that he may not have full control over the military," Mr Choi said. "Rather than going all the way by firing missiles and supervising a missile launch, Kim could be reminding us, 'yes, I'm healthy and I'm still in power'. Leif Eric Easley, an international affairs professor at Ewha University in Seoul, said the shooting could have been aimed at boosting morale in the North Korean military. "The Kim regime may be looking to raise morale of its frontline troops and to regain any negotiating leverage lost during the rumour-filled weeks of the leader's absence," Mr Easley said. "South Korea and the United States should not take lightly such North Korean violations of existing military agreements."