SEOUL, South Korea — Defying rumors that have resurfaced in South Korea of ill health, North Korean leader Kim Jong-un has appeared at the heart of rescue efforts in flood-hit provinces.

Photos and footage showed Mr. Kim in a small inflatable boat on floodwaters, in an SUV traversing a flooded road and speaking to troops at a military helicopter base.

The country’s northeastern province of Pyongan, and the environs of the city of Sinuiju — North Korea’s key transport gateway to China — are suffering from serious monsoon flooding after the Yalu River rose precipitously.

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According to South Korean media, quoting North Korean state media, some 4,100 households have been flooded out, and military operations have rescued some 4,200 civilians from the disaster zone. Mr. Kim replaced his minister for public security during a Workers Party Politbureau emergency meeting held in Sinuiju earlier this week, the reports stated.

On Thursday, South Korea’s Red Cross said it stood ready to provide humanitarian relief and anticipated a “swift response” from the North.  

Kim to the fore

Footage released by state media shows a grim-faced Mr. Kim perched on a small, inflatable boat navigating between half-sunken trees and the thatched roofs of an inundated settlement.

Still images showed him gazing out of the window of an SUV up to its axles in water on a partly flooded road; standing on a landing pad being briefed by military officers in front of a large transport helicopter; and waving at a busload of apparently rescued citizens.

Though no Western journalists are based in North Korea, a number of Western media organizations maintain offices in Pyongyang, staffed by locals, who supply photographic and film content.  

Unlike his late father, Kim Jong-il, who was rarely seen in public, the younger Mr. Kim is P.R.-friendly.

He frequently appears in public and in media — though normally on upbeat occasions, be it greeting cheering citizens, directing a missile launch or driving a tank. He also offers “on the spot guidance” to officials, who scribble their leader’s thoughts down in their notebooks.

His current activities fit his M.O., said one expert.

“He is acting according to the manual: It’s a kind of routine behavior and reaction,” said Kim Kwang-jin, a North Korean defector who works for the state-run think tank the Institute for National Security Strategy in Seoul. “In the past, in such emergency cases, he visits places and tries to be seen leading the actions, solving the trouble and demoting aides. It’s routine.”

Mr. Kim was unconvinced that the North Korean leader was being put at great risk — or suffering great inconvenience.

“You can see that he is wearing a very, very clean white shirt at the flooding disaster scene,” he said. “It is like a show to his own people, without sincerity or real emotion.”

Health rumors resurface

The images of Mr. Kim’s disaster-management efforts were aired just days after South Korea’s National Intelligence Service alleged that Mr. Kim’s obesity is generating health problems.

On Monday, agents briefed the National Assembly, saying that Mr. Kim is suffering from diabetes and high blood pressure as a result of smoking, drinking and stress. The issues are compelling handlers to seek foreign-made medication, they said.

Both Mr. Kim’s predecessors on the North Korean throne suffered health issues. But rumors of the current leader’s ill health, fortified by his periodic disappearances from public view, have circulated multiple times before.

None have had any apparent impact on his governance.

Still, the hefty dictator, who is only 40, was shown in the flood footage being helped down a gentle flight of stone steps to get into the boat.

Also revealed in one still image from the floods was a pack of cigarettes and a glass ashtray placed on a bench beside Mr. Kim in the inflatable boat.