South Korean and US officials say Kim, 66, suffered a stroke. Kim, known to have diabetes and heart disease, has not been seen in public for more than a month.

However, North Korean foreign ministry official Hyun Hak Bong called the reports about Kim's ill health "nonsense spread by bad people who don't wish our republic well".

"Even if they do (spread false speculation about Kim), we are not surprised, and our solidarity will not be broken," Mr Hyun told reporters at the truce village of Panmunjom before meeting South Korean officials about shipping energy aid to the communist nation as part of an international nuclear disarmament pact.

It is the second time North Korean officials have denied Kim is ill. Last week, the country's number two, Kim Yong Nam, and a senior foreign ministry official told Japan's Kyodo News agency that there are "no problems" with the leader and denounced speculation about his health as a "conspiracy plot".

The South Korean government says Kim is recovering. But privately, officials have described it as a "serious health setback" and say he underwent "serious surgery".

US officials also said last week that Kim had suffered a stroke.

South Korea's Dong-a Ilbo newspaper said Washington believed Kim was in "serious" condition, and had not ruled out the possibility that he might be incapacitated.

Washington reached that assessment based on intelligence reports from various spy agencies and shared it with South Korea last weekend, the paper said, citing unidentified diplomatic sources in Seoul and Washington.

Washington saw no sign of a power struggle in the Stalinist nation, the report said.