Kim Jong Il, the enigmatic despot who runs communist North Korea, may have undergone major surgery last month in an operation performed in secret by German doctors.

Reports of a heart bypass operation and failing health have thrown intelligence agencies in the US, China and South Korea into a state of high alert as the region contemplates the spectre of a leaderless, but still nuclear-armed, North Korea.

Sources close to the regime say that the 65-year-old dictator was treated successfully for a blocked artery early last month. He was able to complete a factory visit near North Korea’s border with China three weeks later.

The German Heart Institute Berlin confirmed that it had sent a team of doctors to Pyongyang in May, but said that they were there to treat patients other than Mr Kim.

There have been persistent rumours that Mr Kim’s health is in sharp decline, fuelled by a reduction in the number of his public appearances. Michael Breen, a biographer of Mr Kim, said that speculation was inevitable because of the “huge importance” of the leader’s role in the stability of the region. All the parties involved — the South Koreans, Chinese, Japanese, Americans, and Russians — would be “watching this story very closely.

“So much hinges on the health of this one man. It is of enormous significance to the peninsula if he dies. It could be the beginning of the opening of North Korea or the start of a period of profound instability.”

Mr Kim has yet to clarify what succession plans, if any, are in place. He is thought to be suffering from diabetes, heart problems and high blood pressure. His former personal chef, a Japanese known under the pseudonym Mr Fujimoto, told The Times that from the mid-1980s Mr Kim carried with him a vast array of heart pills and liver drugs.

Mr Kim’s lifestyle has never been conducive to good health. His taste for Japanese beer, whisky and brandy is well known and, Mr Fujimoto said, he would regularly defy medical advice and demand that only the fattiest parts of tuna and mackerel be served.

Although hard evidence for Mr Kim’s physical decline is sparse, recent comments from diplomats based in Pyongyang suggest that he is unable to walk more than a few dozen yards unaided and is accompanied at all times by an attendant carrying a chair so that the “Dear Leader” can rest.

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