Fears were growing for Kim Jong-un’s health today after a US official said the dictator could be in grave danger after heart surgery - although South Korea has played down the reports.

Washington is monitoring intelligence that Kim is in a critical condition after his operation, CNN quoted an unnamed US official as saying.

Kim, 36, was last seen at a government meeting on April 11, and was mysteriously absent from the celebration of his late grandfather Kim Il-Sung’s birthday on April 15.

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