Speculation has recently grown again since Mr Kim, 66, has not been seen in public for more than three weeks. His last outing was August 14, when he reportedly inspected a military unit in North Korea.

A little-known Seoul economics daily, Asia Economy, cited an unnamed government source as saying on Saturday that five Chinese doctors had been in the communist state for more than a week - possibly to treat Mr Kim.

But a spokesman for South Korea's National Intelligence Service told AFP on Sunday that the agency has no information to indicate Mr Kim's health has declined.

'There is no confirmed fact in the report,' the spokesman said, referring to the Asia Economy article.

Foreign media have long speculated that Mr Kim, a former smoker and heavy drinker, was ill. Seoul intelligence officials say they believe he has diabetes and heart problems, but those were not serious enough to affect his job.

Mr Kim strongly denied having heart disease or diabetes at an inter-Korean summit in Pyongyang last October, denouncing media reports about his health as fiction.

North Korea marks the 60th anniversary of its founding on September 9, when Nr Kim usually inspects a military parade outdoors - a potential yardstick to check his health.

Mr Kim has ruled the impoverished state since 1994, when his father and North Korea's founder Kim Il Sung died, creating the world's first communist dynasty.

North Koreans are not allowed to speak about Mr Kim's health in public. -- AFP