North Korean leader Kim Jong-il, died of a heart attack during a train ride, state media reported on Monday, causing immediate concern about who controls the isolated country and its nuclear program.
A black clad hostess said through tears that the leader of 69 years died Saturday due to excessive physical and mental work his way to provide "guidance on the ground".
He suffered a stroke in 2008, but seemed to have recovered. The North's KCNA news agency said that his death occurred at 08.30 local time Saturday (2330 GMT Friday) after "acute myocardial infarction complicated by heart a serious shock."
South Korea, technically still at war with North Korea put its troops and government employees on emergency alert, reported Yonhap news agency. However, the South Korean Defense Ministry said there were no signs of unusual movements of North Korean troops.
"Until tonight, if someone had asked what was the possible scenario under which the North Korean regime would collapse, the answer would have been the sudden death of Kim Jong-il," said Victor Cha, a Korea expert the Centre Strategic and International Studies in Washington.
"So I think we're on that stage and do not know what will be the outcome," he said.
The White House said U.S. President Barack Obama, was notified of the reports on the death of Kim, who is reviewing it carefully and in contact with South Korea and Japan.
The United States is committed to the stability on the Korean peninsula and its allies, said the press secretary of the White House.