Kim Jong-un is in a vegetative state after a failed heart operation, according to Japanese media.
The magazine Shukan Gendai reported that Kim collapsed during a recent visit to a rural part of North Korea and a Chinese medic sent as part of a team to treat Kim believed a delay in a simple procedure to insert a stent left the leader severely ill.
The magazine claims a surgeon in charge of Kim's operation was not used to dealing with obese patients and was too nervous during the op, leading to delays that left Kim in a "vegetative state".
Another report from Hong Kong claims that Kim Jong-un is actually dead.
Vice director of HKSTV Hong Kong Satellite Television Shijian Xingzou says that a "very solid source" has told her Kim Jong-un has died.
On Thursday, US President Donald Trump downplayed reports that Kim was gravely ill. "I think the report was incorrect," Trump told reporters, but he declined to say if he had been in touch with North Korean officials.
On Friday, a South Korean source told Reuters their intelligence was that Kim was alive and would likely make an appearance soon. The person said he did not have any comment on Kim's current condition or any Chinese involvement.
An official familiar with US intelligence said that Kim was known to have health problems but they had no reason to conclude he was seriously ill or unable eventually to reappear in public.
A US State department spokeswoman had no comment. US Secretary of State, Mike Pompeo, when asked about Kim's health on Fox News after Trump spoke said, "I don't have anything I can share with you tonight, but the American people should know we're watching the situation very keenly."
North Korea is one of the world's most isolated and secretive countries, and the health of its leaders is treated as a matter of state security. Reuters has not been able to independently confirm any details on Kim's whereabouts or condition.
North Korea's state media last reported on Kim's whereabouts when he presided over a meeting on April 11. State media did not report that he was in attendance at an event to mark the birthday of his grandfather, Kim Il Sung, on April 15, an important anniversary in North Korea.
Kim, 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.
When Kim Jong Un's father, Kim Jong Il, suffered a stroke in 2008, South Korean media reported at the time that Chinese doctors were involved in his treatment along with French physicians.
Last year, Chinese President Xi Jinping made the first state visit in 14 years by a Chinese leader to North Korea, an impoverished state that depends on Beijing for economic and diplomatic support.
China is North Korea's chief ally and the economic lifeline for a country hard-hit by U.N. sanctions, and has a keen interest in the stability of the country with which it shares a long, porous border.
Kim is a third-generation hereditary leader who came to power after his father Kim Jong Il died in 2011 from a heart attack. He has visited China four times since 2018.
Trump held unprecedented summits with Kim in 2018 and 2019 as part of a bid to persuade him to give up North Korea's nuclear arsenal.