The North Korean leader, Kim Jong-un, has appeared in public for the first time in almost three weeks, according to state media, following speculation that he had been seriously ill following heart surgery. The state news agency KCNA released photographs purportedly showing Kim opening a fertilizer plant in Sunchon, north of the capital Pyongyang. KCNA said Kim, accompanied by other senior officials, including his influential younger sister, Kim Yo-jong, cut a ribbon at a ceremony on Friday. What appeared to be thousands of people attending the event, many of them wearing face masks, released balloons and “broke into thunderous cheers of ‘hurrah!’ for the Supreme Leader,” the agency said. The images showed Kim smiling and talking to aides, as well as touring the plant. The authenticity of the photos, published on the website of the official Rodong Sinmun newspaper, could not be immediately verified. Donald Trump said on Twitter that he he was “glad” Kim had reappeared. “I, for one, am glad to see he is back, and well!” Trump tweeted on Saturday. The North Korean leader was last seen in public on 11 April when he presided over a Workers’ party politburo meeting. State media did not publish a single photograph of Kim for well over two weeks after that date, but carried reports of his daily routine, including diplomatic messages sent to other world leaders. Speculation over his whereabouts gathered pace after he missed the 15 April commemoration of the birthday of his grandfather – and North Korea’s founder, Kim Il-sung – which is the most important event in the country’s political calendar. It was the first time the younger Kim had missed the event since becoming leader. A day earlier, he was not present at the launch of several short-range missiles, despite having personally overseen similar launches in the past. Rumours that Kim, who succeeded his father Kim Jong-il in late 2011, was seriously unwell began with a South Korean report claiming he had undergone a “cardiovascular procedure” at Hyangsan hospital near Pyongyang on 12 April and was recuperating at a villa in nearby Mount Myohyang. Daily NK, a Seoul-based website with secret contacts in the North, claimed Kim’s health had deteriorated since last August due to heavy smoking, obesity and overwork. That report was followed by claims by an unnamed US official, quoted by CNN, that Kim was “in grave danger”. Days later, 38 North, a Washington-based North Korea monitoring project, said it had analysed satellite images it believed showed Kim’s train parked at Wonsan, a resort on the east coast where the leader has a heavily guarded holiday home. But the office of the South Korean president, Moon Jae-in, said it detected no unusual signs in North Korea or any emergency reaction by its ruling party, military and cabinet. Seoul said it believed Kim was still managing state affairs but staying at an unspecified location outside Pyongyang. Defence officials in the US said there was no evidence that Kim had lost control of the country’s military. North Korean media did not offer an explanation for Kim’s absence in Saturday’s report. Last week, the South Korean unification minister Kim Yeon-chul, who oversees engagement with Pyongyang, said it was possible that Kim was taking precautions against the coronavirus outbreak. North Korea continues to claim it has not recorded a single case of Covid-19, despite sharing a border with China, where the outbreak is believed to have started. Harry Kazianis, senior director of Korean studies at the Center for the National Interest think tank in Washington, said the coronavirus theory was plausible. “The most likely explanation for Kim’s absence is with North Korea declaring the coronavirus pandemic an existential threat ... he most likely was taking steps to ensure his health or may have been impacted in some way personally by the virus,” Kazianis said after KCNA released the report. It is not the first time that Kim’s failure to appear in public has triggered speculation about his health. In 2014, he dropped out of sight for nearly six weeks before reappearing with a walking stick. Days later, South Korea’s spy agency said he had undergone surgery to remove a cyst from his ankle.