Media playback is unsupported on your device Media caption The BBC's Lucy Williamson says news of the death has taken people by surprise 
 
 North Korean leader Kim Jong-il has died of a heart attack at the age of 69, state media have announced. 
 
 Millions of North Koreans were "engulfed in indescribable sadness", the KCNA state news agency said, as people wept openly in Pyongyang. 
 
 KNCA described one of his sons, Kim Jong-un, as the "great successor" whom North Koreans should unite behind. 
 
 Pyongyang's neighbours are on alert amid fears of instability in the poor and isolated nuclear-armed nation. 
 
 This could be a turning point for North Korea William Hague, UK Foreign Minister World reactionDeath triggers swift reaction 
 
 Fears were compounded by unconfirmed reports from South Korean news agency Yonhap that the North had test-fired a missile off its eastern coast before the announcement of Kim Jong-il's death was made. 
 
 Unnamed government officials in Seoul were quoted as saying they did not believe the launch was linked to the announcement. The South Korean defence ministry has declined to comment. 
 
 Following news of Mr Kim's death, South Korea put its armed forces on high alert and said the country was on a crisis footing. Japan's government convened a special security meeting. 
 
 China - North Korea's closest ally and biggest trading partner - expressed shock at the news of his death and pledged to continue making "active contributions to peace and stability on the Korean peninsula and in this region". 
 
 Asian stock markets fell after the news was announced. 
 
 Crying aloud 
 
 Mr Kim's death was announced in an emotional statement on national television. 
 
 Analysis North Korea has shocked the world by announcing that its leader has died. Kim Jong-il had been presented to his people as a father-figure and demi-god - all-powerful and benevolent. But his tight control of the country, and his creation of a nuclear arsenal, has meant his death has caused political shockwaves around the region too. His presumed successor, Kim Jong-un, is largely unknown outside the secretive state, and countries throughout the region are watching closely for any instability in the transition of power. 
 
 The announcer, wearing black, struggled to keep back the tears as she said he had died of physical and mental over-work. 
 
 The KCNA later reported that he had died of a "severe myocardial infarction along with a heart attack" at 08:30 local time on Saturday (23:30 GMT Friday). 
 
 He had been on a train at the time, for one of his "field guidance" tours, KCNA said. 
 
 The state news agency said a funeral would be held in Pyongyang on 28 December and Kim Jong-un would head the funeral committee. A period of national mourning has been declared from 17 to 29 December. 
 
 Images from inside the secretive state showed people in the streets of Pyongyang weeping at the news of his death. 
 
 Ruling party members in one North Korean county were shown by state TV banging tables and crying out loud, the AFP news agency reports. 
 
 "I can't believe it," a party member named as Kang Tae-Ho was quoted as saying. "How can he go like this? What are we supposed to do?" 
 
 Another, Hong Sun-Ok, said: "He tried so hard to make our lives much better and he just left like this." 
 
 KCNA said people were "convulsing with pain and despair" at their loss, but would unite behind his successor Kim Jong-un. 
 
 "All party members, military men and the public should faithfully follow the leadership of comrade Kim Jong-un and protect and further strengthen the unified front of the party, military and the public," the news agency said. 
 
 Little is known about Kim Jong-un. He was educated in Switzerland, is aged in his late 20s and is believed to be Kim Jong-il's third son - born to Mr Kim's reportedly favourite wife, the late Ko Yong-hui. 
 
 Kim Jong-un was unveiled as his father's likely successor just over a year ago. Many had expected to see this process further consolidated in 2012. 
 
 'Turning point' 
 
 South Korea - which remains technically at war with the north - urged people to "go about their usual economic activities" on Monday, while putting the military on alert. 
 
 President Lee Myung-Bak spoke to US President Barack Obama by telephone and they "agreed to closely co-operate and monitor the situation together", a South Korean presidential spokesman said. 
 
 Reaction from Washington was muted, with the White House saying it was "closely monitoring" reports of the death. 
 
 The US remained "committed to stability on the Korean peninsula, and to the freedom and security of our allies", it said in a statement. 
 
 China said it was "distressed" to hear the news of his death. "We express our grief about this and extend our condolences to the people of North Korea," foreign ministry spokesman Ma Zhaoxu was quoted by Xinhua news agency as saying. 
 
 Analysis Kim Jong-il's death should not have come as a complete surprise to anyone, given his tenuous health. But it is safe to say that the North Koreans would have very much preferred that he lived one more year, so that in 2012, the 100th anniversary of the birth of Kim Il-sung, his father, Kim Jong-il would have been on hand to pay homage to "the Great Leader". Now that lot will fall to Kim Jong-un, Kim Jong-il's youngest son who has been put forward as the natural and fully prepared successor to his father. Will Kim's death aid ties with US? 
 
 Analysts say that with the process of transition from father to son incomplete, Mr Kim's death could herald "very unstable times" in North Korea. 
 
 "We have to be very worried because whenever there is domestic instability North Korea likes to find an external situation to divert the attention away from that - including indulging in provocation," Professor Lee Jung-hoon, specialising in international relations at Yonsei University in Seoul, told the BBC. 
 
 Christopher Hill, former US representative to the six-party talks on North Korea's nuclear programme, said all parties needed to "keep cool heads". 
 
 Britain's Foreign Secretary William Hague said it could be a "turning point" for North Korea to engage more closely with the international community. 
 
 Kim Jong-il inherited the leadership of North Korea from his father Kim Il-sung. 
 
 Shortly after he came to power in 1994, a severe famine caused by ill-judged economic reforms and poor harvests left an estimated two million people dead. 
 
 His regime has been harshly criticised for human rights abuses and is internationally isolated because of its pursuit of nuclear weapons. 
 
 Under Mr Kim's leadership, funds have been channelled to the military and in 2006 North Korea conducted its first nuclear test. It followed that up with a second one three years later. Multinational talks aimed at disarming North Korea have been deadlocked for months. 
 
 He had reportedly been in poor health since suffering a stroke in August 2008. ||||| SEOUL The world watched anxiously on Wednesday as North Korea staged a huge funeral in the capital, Pyongyang, for former leader Kim Jong-il, searching for signs of what to expect from the isolated nation that may be close to attaining nuclear weapons capacity. 
 
 Bleak pictures from state television showed a funeral cortege led by a limousine carrying a huge picture of the 69-year-old, who died on December 17, passing serried ranks of olive green-clad soldiers whose bare heads were bowed in homage in the main square of the snow-covered capital. 
 
 A hearse carrying the coffin was led by a weeping Kim Jong-un, the son and heir, accompanied by Jang Song-thaek, his uncle and a key power-broker in the transition, and Ri Yong-ho, the army chief of staff. 
 
 "Seeing this white snow fall has made me think of the general's efforts and this brings tears to my eyes," Seo Ju-rim, a red-cheeked, weeping female soldier, told North Korean television, referring to the late Kim. 
 
 One of the myths surrounding Kim Jong-il was that he could control the weather and state media has reported unusually cold and wild weather accompanying his death. 
 
 Video showed weeping civilians who swayed with grief and shouted "father, father" as black Lincoln and Mercedes limousines and army trucks streamed past the crowds. It was not clear whether the pictures were live or recorded, although a state television announcer said it had been carried live. 
 
 "I wished it was a dream, how can this be true," sobbed one middle-aged woman named Kim. "How can anything like this ever happen in the world?" 
 
 At one stage, weeping women were held back by men who linked arms to prevent them surging towards the cortege. The procession ended after about three hours with 21 guns fired in salute as the top leadership looked on from a podium. 
 
 Kim Jong-un will become the third member of the family to run the unpredictable North Asian country as it enters 2012, the year that was supposed to mark its self-proclaimed transformation into a "strong and prosperous" nation. 
 
 The North has conducted two nuclear tests and Larry Niksch, who has tracked North Korea for the non-partisan U.S. Congressional Research Service for 43 years, believes it could take as little as one to two years to have a working nuclear missile once it produced enough highly enriched uranium for the warhead's core fuel. 
 
 The prospect of an untested leader, believed to be in his late 20s, having nuclear capacity has alarmed many. 
 
 "Yes, we are watching and will be analyzing how any changes can be reflected in our policy," a South Korean government official said. He was not authorized to speak to the media, so could not be identified. 
 
 UNCLE JANG, POWER BEHIND THE THRONE 
 
 State television showed Jang Song-thaek walking directly behind Kim Jong-un alongside the limousine carrying the coffin. Jang ranked a lowly 19th in the list of names on the state funeral committee but his public elevation confirmed that he will play a key role in shaping policies. 
 
 An ascetic-looking, bespectacled 65-year-old, Jang has overcome a purge, bitter palace intrigue and personal tragedy to become vice chairman of the National Defense Commission, the supreme leadership council which Kim Jong-il led as head of the military state. 
 
 "Kim Jong-un is clearly the head of the new leadership but, in terms of hierarchy and influence, Jang appears to have secured considerable position," said Yoo Ho-yeol, a North Korea expert at Korea University in the South. 
 
 Strong it may be -- North Korea is backed by neighboring China and has a 1.2 million-strong armed forces -- but prosperous it is not. 
 
 On average, the 25 million North Koreans have a life expectancy 3-1/2 years lower than they did when "Eternal President" Kim Il-sung, the new leader's grandfather, died in 1994, according to U.N. data. 
 
 The United Nations, in a country program for 2011-15, says North Korea's main challenge is to "restore the economy to the level attained before 1990" and to alleviate food shortages for a third of its people. 
 
 Indications from the transition suggest Kim Jong-il's "military first" policy will continue, meaning the military gets the lion's share of scare resources and further hardship for the majority in a country that endured starvation in the 1990s. 
 
 Pyongyang's affirmation of the "songun" (military first) policy is a strong indicator that North Korea's policies won't change under Jong-un," said analyst Bruce Klingner of the Heritage Foundation, a conservative Washington think tank. 
 
 "As such, speculation that the new leader will be more amenable to reform and to a less belligerent foreign policy since he studied in Switzerland in his youth, will prove short-lived," he said after the funeral. 
 
 Leverage from outside, with the exception of China, is limited. All the United States, South Korea and Japan can do is hope that the regime does not collapse, nor flex its military muscle as it did in 2010, when it shelled a South Korean island. 
 
 North Korea was established in 1948 and under its founding father, Kim Il-sung, went to war to try to conquer the South. It failed and in 1953 a dividing line that would become the world's most militarized frontier was drawn across the peninsula. 
 
 PROSPECTS OF A PURGE 
 
 While Kim Il-sung was revered by his people for fighting Japanese colonial rule, the halo over his successors has steadily dimmed to such an extent that his grandson, the new ruler, will have to rely on people such as his uncle, Jang, to hold on to power, at least in the short term. 
 
 Official media in the North have built Kim Jong-un, a jowly and rotund man in his late 20s, into a leader worthy of inheriting the crown, naming him "respected general", "great successor", "outstanding leader" and "supreme commander". 
 
 This year, dissident groups based in South Korea, citing North Korean refugees and businessmen working in China, linked the youngest Kim to a crackdown on business activities and a tougher policy on people seeking to flee from North Korea. 
 
 Those reports could not be verified independently, but would again suggest that under the new man, further repression is more likely than an economic opening. 
 
 It also gives little hope for the 200,000 North Koreans who human rights group Amnesty international says are enslaved in labor camps, subjected to torture and hunger or execution. 
 
 "There is likely to be a politically motivated purge and imprisonment, and it could go on for a considerable period of time," said Pak Sang-hak, who heads a group in Seoul working to support defectors, and is himself a defector. 
 
 "That is especially because of the relative instability of Kim Jong-un's leadership. There might also be persecution as a way of intimidation and discipline." 
 
 (Additional reporting by Christine Kim and Iktae Park in SEOUL and Jim Wolf and Paul Eckert in WASHINGTON; Editing by Jonathan Hopfner, Robert Birsel and Eric Beech)
– Kim Jong Il, North Korea's mercurial and enigmatic leader, has died at the age of 69, according to state television. His death was was announced today by a tearful announcer in black who said he had died from physical and mental over-work while on a train trip to a location outside Pyongyang, Reuters reports. A later report from state-run media said the "Dear Leader" had died of heart failure. Kim, revered as a man of almost superhuman talents by state-run media, but widely mocked in the West, inherited power after his father's death in 1994. His designated successor is believed to be his son, Kim Jong Un, who is still in his 20s. Asian stock markets fell on the news of his death and South Korea placed its military on alert. With the transition to power in North Korea incomplete, "very unstable times" times could lie ahead for the diplomatically isolated nation, an analyst tells the BBC.