Pyongyang, Dec 19 (IANS): Kim Jong-il, the 69-year-old supreme leader of nuclear-armed North Korea, died Saturday during a train journey. His youngest son was made the "great successor", the country's official KCNA news agency announced Monday.
South Korea promptly put its security forces on high alert as its financial market got rocked. Washington said it was in touch with Seoul and Tokyo over North Korean developments, reports Xinhua.
The KCNA said that the "Korean revolution" is now led by his son Kim Jong-un, and that the powerful "Workers' Party of Korea (WPK) members, servicepersons and all other people will be faithful to his leadership".
Kim Jong-un is the youngest son of Kim Jong-il and his late third wife Ko Yong-hui.
KCNA urged the communist nation to rally behind the younger Kim, who is believed to have been groomed to take over power and was appointed a general last year.
Kim died "from a great mental and physical strain at 08.30 Dec 17, 2011, on train during a field guidance tour", said the official media report.
Kim, who had received medical treatment for his cardiac diseases for a long period, suffered "an advanced acute myocardial infarction, complicated with a serious heart shock" on the train, reported Xinhua.
Kim had taken power in 1994 following the death of his father, Kim Il-sung.
Kim built a nuclear arsenal, which culminated in North Korea's first nuclear test explosion in 2006. Another test took place in 2009.
He led the country of an estimated population of 24 million with an iron hand.
The funeral for Kim Jong-il will be held in Pyongyang Dec 28, with the mourning period lasting till Dec 29. No foreign delegations will be allowed to attend the funeral.
Kim's body was laid in a massive mausoleum in Pyongyang where his father, Kim Il-sung, lies in state in a glass case.
Experts were of the opinion that the succession of the youngest son may not be easy.
"The handover to Jong-un might look smooth from the outside, but there is considerable doubt over the loyalty of insiders who may have been waiting for the late Kim's passing to seize power ahead of the undistinguished son in his late 20s," guardian.co.uk quoted Sean Callow, a senior currency strategist at Westpac Banking in Sydney, as saying.
South Korea was in a state of high alert Monday following Kim's death.
South Korea's Joint Chiefs of Staff (JCS) put the military on alert and called an emergency meeting.
Authorities have stepped up border surveillance, according to Seoul-based Yonhap News Agency. North Korea has a 1.2 million strong army.
The US too swung into action and was in close touch with South Korea and Japan over Kim's death.
The White House said it remains committed to stability in the Korean peninsula.
"We are closely monitoring reports that Kim Jong Il is dead," White House spokesperson Jay Carney said in a statement.
"The president (Barack Obama) has been notified, and we are in close touch with our allies in South Korea and Japan," Xinhua quoted him as saying.
"We remain committed to stability on the Korean peninsula, and to the freedom and security of our allies."
North Korea is one of the world's most centrally directed and least open economies. It faces chronic economic problems.
Large-scale military spending has drawn off resources needed for investment and civilian consumption. Industrial and power output have stagnated for years at a fraction of pre-1990 levels.
Frequent weather-related crop failures aggravated chronic food shortages caused by on-going systemic problems, including a lack of arable land, collective farming practices, poor soil quality and acute shortage of tractors and fuel, according to experts.