North Korea’s Kim Jong-un has made his first public appearance in nearly three weeks, state media reported on Saturday, following intense speculation that the leader of the nuclear-armed nation was seriously ill or possibly dead.

State television showed Kim walking, smiling broadly and smoking a cigarette at what the North said was the opening of a fertiliser factory on Friday in South Pyongan province’s Sunchon city, north of Pyongyang.

US subscription-based website NK News noted that the video footage showed that Kim had what looked to be a new scar on his inner right wrist.

It quoted US medical professionals as saying: “It looks like a right radial artery puncture . . . [which is] often used for access to the coronary arteries for stent placement.”

Noting that the mark appeared to be “about a week old”, the professional said: “It is hard to tell from the foreshortening of the photograph, but it seems a bit medial . . . It is not an IV [intravenous], which wouldn’t leave such a mark.”

A South Korean surgeon told NK News that the mark on Kim’s arm “looks more plausible to be a procedure or check-up mark from a procedure on a heart-related issue.”

Jason H Wasfy, a cardiologist at Massachusetts General Hospital and Assistant Professor at Harvard Medical School, told NK News: “From these pictures, this dot is not likely to be a radial puncture site. The position would be wrong and the appearance would be unusual.

“So I think this is not likely [a radial puncture] based on these pictures. It normally would be closer to the thumb.”

Rumours about Kim’s health have been swirling since his conspicuous no-show at April 15 celebrations for the birthday of his grandfather, the North’s founder – the most important day in the country’s political calendar.

His absence triggered a series of fevered rumours and unconfirmed reports over his condition, while the US and South Korea insisted they had no information to believe any of the conjecture was true.

Seoul’s unification ministry reacted to Saturday’s report by saying “groundless” speculation about Kim had caused “unnecessary confusion”, calling for more careful consideration in future.

Kim’s sudden death would have left Pyongyang facing an unplanned succession for the first time in its history and raised unanswered questions over who would succeed him and take over the North’s nuclear arsenal.

China, the North’s key diplomatic ally and main provider of trade and aid, is keen to maintain stability in its neighbour and avoid the possibility of an influx of refugees.

North Korea is “at the epicentre of an extremely tense security crisis”, involving “a nuclear standoff where tens of millions of lives are at stake,” Henri Feron, Senior Fellow at the US Center for International Policy, said.

“This raises legitimate concerns about the domestic and international instability that his death could cause.”

US President Donald Trump on Saturday said he was “glad” about the reappearance of Kim and that the North Korea leader is healthy. “I, for one, am glad to see he is back, and well!” Trump tweeted.

Footage showed Kim in his trademark black suit, waving to hundreds of workers who cheered his appearance and released balloons.

He was flanked by senior officials – including his sister and close adviser Kim Yo-jong – and showed no outward signs of ill health.

At one point Kim sat in front of a sign that described the event as a factory opening ceremony for May 1, 2020, but his appearance could not be independently verified.

As with previous public appearances during the global coronavirus pandemic, Kim and his entourage were not wearing masks, unlike the crowd of workers at the ceremony.

Analysts said Kim could not appear in public wearing a mask as it would make him appear vulnerable to the North Korean people.

The North has insisted that it has not seen a single case of coronavirus, although experts say that is unlikely.

Daily NK, a Seoul-based online media outlet run mostly by North Korean defectors, reported on April 23 that a North Korean man who crossed the Tumen River in North Hamgyong province into China’s Jilin province on April 20 tested positive for Covid-19.

Having been shot by a Chinese border guard, he was transferred to a hospital in the province’s Longjing city where he was placed under quarantine and underwent medical tests for the virus, said Daily NK.

Other Daily NK reports have suggested that 180 soldiers may have died from “coronavirus-like symptoms” between January and February, and that 23 other people may have died in the country due to the disease as of late February.

Kim’s repeated appearances without a mask had led some to speculate that he may have caught the virus.