North Korean leader Kim Jong-il (67) has life-threatening pancreatic cancer, South Korean broadcaster YTN said on Monday.
Some South Korean and United States internet sites were down or slowed to a crawl for a third day on Thursday after attacks by a hacker.
The leaders of South Korea and the United States told North Korea to drop its atomic ambitions and stop threatening the region.
North Korea said on Monday it had found two US journalists guilty of entering the state illegally and sentenced both to 12 years of hard labour.
The United States has told South Korea it is preparing financial measures to punish North Korea for illicit weapons trade.
South Korea’s chief prosecutor quit on Thursday to take responsibility for leading a graft probe into former president Roh Moo-hyun.
Kim Jong-il is too worried about his own well-being to start a war, North Korean defectors said on Thursday.
North Korea, defiant in the face of international condemnation of its latest nuclear test, on Tuesday accused the United States of hostile intent.
North Korea on Wednesday threatened to conduct a nuclear test unless the UN Security Council apologises for imposing sanctions against it.
North Korea will put two US journalists arrested last month on its border with China on trial to face criminal charges, its media said on Friday.