Pyongyang marked the birthday of its late founder, Kim‘s grandfather Kim Il Sung, on April 15 – by far the most important date in its annual political calendar – but Kim was not seen in attendance.

Daily NK, an online media outlet run mostly by North Korean defectors, said Kim had undergone a cardiovascular procedure earlier this month and was recovering at a villa in North Phyongan province.

“Excessive smoking, obesity, and fatigue were the direct causes of Kim’s urgent cardiovascular treatment,” it cited an unidentified source inside the country as saying.

No confirmation of the report was immediately available.

But it triggered widespread speculation, with CNN citing a US official saying that Washington was “monitoring intelligence” that Kim was in “grave danger after a surgery”. The report did not specify what the intelligence was.

In a statement, a spokesman for the South’s presidential Blue House said: “We have nothing to confirm and no special movement has been detected inside North Korea as of now”.

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