North Korean leader Kim Jong-il, 67, has life-threatening pancreatic cancer, South Korean broadcaster YTN said today, citing information gathered from Chinese and South Korean intelligence sources.

The report raises questions about leadership in Asia's only communist dynasty and who will make decisions concerning its nuclear programmes.

Kim's health is one of the most closely guarded secrets in the reclusive state but he is widely thought to have suffered a stroke a year ago, although there has never been official confirmation.

YTN said the diagnoses of the cancer came around the same time as the stroke.

A gaunt Kim with thinning hair made a rare public appearance last Wednesday at a memorial for his father and state founder Kim Il-sung. The stark figure he cast furthered speculation he was still ill.

South Korea's National Intelligence Service could not immediately comment on the report, nor could U.S. officials.

South Korean financial markets took the YTN report with caution, saying it cast a shadow over sentiment.

"Such news highlights South Korea's geopolitical uncertainty and risks and one thing that investors hate is any uncertainty," said Lee Kyoung-su, a market analyst at Taurus Investment & Securities.

North Korea has been raising tension in Asia through missile launches and a nuclear test on May 25 which was met by U.N. sanctions aimed at cutting off it arms trade, one of its few sources of hard cash.

South Korean officials said this military grandstanding was aimed at helping Kim build internal support as he prepares for succession, with his youngest son seen as the likely heir.