A South Korean television station reports that North Korean leader Kim Jong Il has pancreatic cancer, and that his illness is life-threatening. YTN television says its report is based on information obtained by South Korean and Chinese intelligence officials.

However, it is far from certain such reports can be considered reliable, says former CNN correspondent Mike Chinoy, author of Meltdown: The Inside Story of the North Korean Nuclear Crisis. ?The way information leaks out of South Korea is very prone to manipulation," he said.

"You have the South Korean intelligence service, which is highly politicized, which has a conservative bent," said Chonay.  "Clearly, they know a lot, but they have a long track record of manipulating what they know for their own political purposes. These leaks tend to come to South Korean media who lap them up uncritically, put them out, then get picked up by the international media and take on a life of their own when it?s very unclear that there is any substance to it.?

Mr. Kim's health has been a focus of speculation for the past year after he reportedly suffered a stroke. He disappeared from public last August for several months. North Korean media outlets have strongly denied the reports of Mr. Kim's ill health, and published undated photos and video footage of him.  

The status of Mr. Kim's health raises the issue about his succession in the communist dynasty, and who will control the country's nuclear weapons programs. Recent media reports said Mr. Kim named his youngest son, Kim Jong Un, 26, as his successor.  In April, he promoted his brother-in-law Jang Song Thaek to the powerful national Defense Commission.