A special train that may belong to North Korean leader Kim Jong-un was seen last week at a resort town in the country amid conflicting reports about his health and whereabouts. On Saturday, 38 North, a project based in Washington that monitors North Korea, said the train was parked at the "leadership station" in the eastern city of Wonsan on April 21 and April 23. The station is reserved for the use of the Kim family, 38 North. The group said it was probably Mr Kim's train, but it was unknown whether he was in Wonsan. "The train's presence does not prove the whereabouts of the North Korean leader or indicate anything about his health," the report said. "But it does lend weight to reports that Kim is staying at an elite area on the country's eastern coast." Speculation about Mr Kim's health first arose due to his absence from the anniversary of the birthday of North Korea's founding father and his grandfather, Kim Il-sung, on April 15. North Korea's state media most recently reported on Mr Kim's whereabouts when he presided over a meeting on April 11. China has sent a team to North Korea, including medical experts. A third-generation leader who came to power after the death of his father, Kim Jong-il, in 2011, Mr Kim has no clear successor in a nuclear-armed country that could present major international risk. On Thursday, US President Donald Trump played down reports that Mr Kim was ill. "I think the report was incorrect," Mr Trump said. He would not say whether he had been in touch with North Korean officials. Mr Trump has met Mr Kim three times to try to persuade him to give up a nuclear weapons programme that threatens the US and North Korea's Asian neighbours. While talks have stalled, Mr Trump continued to suggest Mr Kim was a friend. Last Monday, Daily NK, a South Korean website that reports on its neighbour, quoted an unidentified source in North Korea as saying Mr Kim underwent medical treatment in the resort county of Hyangsan, north of North Korea's capital Pyongyang. It said he was recovering from a cardiovascular procedure on April 12. Since then, South Korean media reports have quoted unidentified sources as saying Mr Kim might be staying in the Wonsan area. On Friday, local news agency Newsis said South Korean intelligence sources reported that a special train for Mr Kim's use was seen in Wonsan, while his private plane remained in Pyongyang. Newsis reported Mr Kim may be sheltering from Covid-19. Mr Kim, who is believed to be 36, has disappeared from coverage in North Korean state media before. In 2014, he vanished for more than a month and North Korean state TV later showed him walking with a limp. Speculation about his health has been fanned by his heavy smoking, apparent weight gain since taking power and family history of cardiovascular problems.