Kim Jong Un
Kim Jong Un Reuters

A South Korean official on Sunday poured cold water on mounting speculation about the health of North Korea's leader Kim Jong Un, telling CNN he is "alive and well."

"Our government position is firm," Moon Chung-in, the top foreign policy adviser to South Korean President Moon Jae-in, told the network.

"Kim Jong Un is alive and well. He has been staying in the Wonsan area since April 13. No suspicious movements have so far been detected," added the South Korean official.

Last week it was reported that Kim is in grave danger after undergoing heart surgery. The report was denied by a South Korean official.

Subsequent reports claimed the North Korean leader is in a vegetative state.

Kim last appeared in North Korean state media on April 11 but missed the celebration of his grandfather's birthday on April 15, which raised speculation about his well-being.

A US official told CNN last week that the concerns about Kim's health are credible, but their severity is hard to assess.

It followed a report by Daily NK, an online newspaper based in South Korea that focuses on North Korea, that Kim reportedly received a cardiovascular procedure because of "excessive smoking, obesity, and overwork."

It added that the leader is now receiving treatment in a villa in Hyangsan County. After assessing that Kim's condition had improved, most of the medical team treating him returned to Pyongyang on April 19 while some of them remained to oversee his recovery, according to the news site. CNN was unable to independently confirm the report.

On Sunday, though, North Korean state newspaper Rodong Sinmun said Kim sent thanks to workers who helped in remodeling the city of Samjiyon in North Korea. CNN could not independently confirm the authenticity of Sunday's report either.

Senator Lindsey Graham (R-SC), meanwhile, speculated that the rumors about Kim are likely true.

Speaking on Fox News, Graham said he would be “shocked” if Kim were alive and well, arguing that if the North Korean leader were healthy enough to make a public appearance or statement, he would do so to dispel the rumors surrounding his condition.