The U.S. is monitoring reports that North Korean leader Kim Jong Un Kim Jong UnSatellite images indicate North Korea preparing for massive military parade South Korea warns of underwater missile test launch by North Korea Trump says he didn't share classified information following Woodward book MORE is in grave condition after undergoing surgery, a U.S. official told CNN on Monday.

South Korea’s Yonhap news agency, however, cited a government official there who said the reclusive leader was not seriously ill.

The conflicting reports come after Reuters cited a news outlet run mostly by North Korean defectors based in South Korea on Monday evening claiming Kim was recovering after a cardiovascular procedure.

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“My understanding is that he had been struggling [with cardiovascular problems] since last August but it worsened after repeated visits to Mount Paektu,” one unidentified source told the South Korean news outlet.

The website also noted that Kim, 36, was not seen at recent celebrations on April 15 marking the birthday of his grandfather Kim Il Sung, the founder of North Korea's modern dictatorship.

The Daily NK report further claimed that Kim has faced health issues in recent months due to obesity, smoking and stress, according to Reuters.

The country recently conducted a weapons test on the eve of parliamentary elections in neighboring South Korea that reportedly were part of the birthday celebrations.