Image copyright Reuters Image caption Kim Jong-un has received numerous official titles since becoming North Korea's leader 
 
 Kim Jong-un took on the mantle of North Korea's supreme leadership with little political or military experience behind him. 
 
 Kim Jong-il, North Korea's "Dear Leader", was in the process of grooming him as his successor when he died in December 2011. 
 
 Immediately after his father's death, the younger Kim was hailed as "the great successor". He was named head of the party, state and army within a fortnight of his father's death. 
 
 Since then, he has shown he is committed to the advancement of North Korea's weapons programme, ordering four nuclear tests and several missile tests. 
 
 He has also shown himself to be ruthless with the purge of his powerful uncle and the murder, widely attributed to an order from him, of his half-brother. 
 
 'Morning Star King' 
 
 Kim Jong-un, the youngest son of Kim Jong-il and his third wife Ko Yong-hui, was born in 1983 or 1984. 
 
 Image copyright AFP Image caption The undated image shows Kim Jong-un as a student in Switzerland 
 
 He was initially not thought to be in the frame to take up his father's mantle. Analysts focused instead on his older half-brother Kim Jong-nam and older full brother Kim Jong-chol. 
 
 However Kim Jong-nam's deportation from Japan in May 2001 and middle brother Kim Jong-chol's reported "unmanliness" improved his chances. 
 
 Analysts saw him as the coming man after he was awarded a series of high-profile political posts. 
 
 Swiss-educated like his brothers, Kim Jong-un avoided Western influences, returning home when not in school and dining out with the North Korean ambassador. 
 
 After his return to Pyongyang, he is known to have attended the Kim Il-sung Military University. 
 
 His mother was thought to be Kim Jong-il's favourite wife, and she clearly doted on her son, reportedly calling him the "Morning Star King". 
 
 In August 2010, when Kim Jong-il visited China, one report said Kim Jong-un had accompanied his father on the trip. By then he was widely seen as the heir-apparent and when Kim Jong-il died, this was quickly confirmed. 
 
 Military-first 
 
 Mr Kim made his first public speech as North Korea marked the 100th anniversary of the birthday of founder Kim Il-sung on 15 April 2012, praising the "military first" doctrine and vowing the time his nation could be threatened was "forever over". 
 
 Image copyright KCNA Image caption State media showed Kim Jong-un in a celebratory mood following the launch of a ballistic missile in July 2017 
 
 Image copyright KCNA Image caption Factory inspections are the mainstay of the North Korean leader's domestic media appearances 
 
 Under him, the development of North Korea's nuclear and missile programmes has continued and appears to have made rapid strides. Four more nuclear tests have taken place, bringing the regime's total to six. 
 
 Pyongyang claims it has successfully tested a miniaturised hydrogen bomb that could be loaded on to a long-range missile, but experts remain divided on how advanced its programme is. 
 
 The reach of North Korea's missiles also appears to have increased. In 2017 the regime test-fired several missiles, and claimed it had tested intercontinental ballistic missiles that could reach the US - leading to a surge in tensions with the Donald Trump-led administration and an intensified UN sanctions regime. 
 
 As the animosity between the two sides rose, Mr Trump and Mr Kim engaged in an increasingly fiery war of words. 
 
 Media playback is unsupported on your device Media caption Donald Trump and Kim Jong-un: From enemies to frenemies? 
 
 Mr Trump called the North Korean leader a "rocket man on a suicide mission" while Mr Kim called the US leader a "mentally deranged US dotard". 
 
 Yet, unexpectedly, Mr Kim offered an olive branch to South Korea in his new year's address, saying he was "open to dialogue" and might send a team to the February 2018 Winter Olympics in South Korea. 
 
 A flurry of diplomatic activity followed, with the two Koreas marching under one flag in the Olympic opening ceremony, and high-level meetings taking place between the two sides. 
 
 Two milestone meetings have now been planned: a summit between Mr Kim and his South Korean counterpart Moon Jae-in in late April, and a face to face meeting between Mr Kim and Mr Trump in May - the first of its kind between sitting US and North Korean leaders. 
 
 Ahead of the two summits, Mr Kim made his first known foreign trip as leader. He took a train to Beijing - North Korea's main ally and trading partner. 
 
 Media playback is unsupported on your device Media caption Chinese TV showed footage of the two leaders with their wives 
 
 In April, Kim Jong-un said he had suspended all missile tests and would shut down a nuclear test site, because his country had achieved "nuclear weaponisation". 
 
 Although the halt was welcomed internationally, observers pointed out that Pyongyang had not pledged to get rid of its existing weapons, and has previously broken promises to halt nuclear development. 
 
 Meet the Kims 
 
 Image copyright AFP Image caption Mr Kim and Ms Ri are thought to have three children 
 
 Domestically, Mr Kim's repeated replacement of defence ministers - there have been at least six men in the post since 2011 - has been seen by some analysts as an indication of his lack of confidence in the loyalty of the armed forces. 
 
 And the most high-profile indication of a possible power struggle within the North Korean elite came in December 2013, when Kim Jong-un ordered the execution of his uncle Chang Song-thaek. State media said he had been plotting a coup. 
 
 Mr Kim is also widely believed to have ordered the murder of his exiled half-brother, Kim Jong-nam, in February 2017 at Kuala Lumpur International Airport. 
 
 Not much was known of Mr Kim's personal life until television footage of an unidentified woman attending events with him surfaced. In July 2012, state media announced that Mr Kim was married to "Comrade Ri Sol-ju". 
 
 Image copyright AFP Image caption Kim Yo-jong, Mr Kim's sister, holds a senior post in the Workers' Party of Korea 
 
 Little is known of Ms Ri, but her stylish appearance led some analysts to suggest that she was from an upper-class family. Reports have suggested that Ms Ri may have been a singer who caught Mr Kim's attention during a performance. 
 
 According to South Korean intelligence, the couple have three children. 
 
 Mr Kim's sister, Kim Yo-jong, holds a senior post in the Workers' Party of Korea - and stole the limelight when she represented her brother at the Winter Olympics in the South. It is not known whether his elder brother, Kim Jong-chol, holds an official role. ||||| North Korea on Monday urged its 24 million people to rally behind 20-something heir-apparent Kim Jong Un as the nation mourned the death of supreme leader Kim Jong Il. 
 
 FILE - In this April 25, 2002 file photo, North Korean leader Kim Jong Il claps from the balcony as soldiers salute him during a military parade, celebrating the foundation of the armed forces in Pyongyang,... (Associated Press) 
 
 FILE - In this Oct. 10, 2010 file photo Kim Jong Un, right, along with his father and North Korea leader Kim Jong Il, left, attends during a massive military parade marking the 65th anniversary of the... (Associated Press) 
 
 South Korea, meanwhile, put its military on high alert, while people in the streets of Pyongyang broke into tears as they learned the news that Kim had died at the age 69 of heart failure. The United States said it was in close contact with allies South Korea and Japan. 
 
 The North's official Korean Central News Agency said the country, people and military "must faithfully revere respectable comrade Kim Jong Un." 
 
 "At the leadership of comrade Kim Jong Un, we have to change sadness to strength and courage and overcome today's difficulties," it said. 
 
 Kim Jong Il unveiled his third son Kim Jong Un as his successor a year ago, putting him in high-ranking posts. Little is known about the younger Kim, who is believed to be in his 20s. 
 
 Kim Jong Un regularly accompanied his father on trips around the country over the past year. Kim Jong Il inherited power after his father, revered North Korean founder Kim Il Sung, died in 1994. 
 
 South Korea's police were placed on a high alert after Kim's death, according to the National Police Agency, and the South Korean parliament convened emergency committee sessions on national defense, intelligence and unification affairs. South Korean President Lee Myung-bak put the military on alert and convened a national security council meeting. 
 
 The South Korean and U.S. militaries have bolstered reconnaissance and are sharing intelligence assets on North Korea, according to Seoul's Defense Ministry. About 28,500 U.S. troops are stationed in South Korea. 
 
 The White House said in a statement that it is closely monitoring reports of Kim's death. 
 
 "The president has been notified, and we are in close touch with our allies in South Korea and Japan. We remain committed to stability on the Korean peninsula, and to the freedom and security of our allies," the statement said. 
 
 The North said it would place Kim's body in the Kumsusan memorial palace in Pyongyang and would hold a national mourning period until Dec. 29. Kim's funeral will be held on Dec. 28, it said. 
 
 In a "special broadcast" Monday from the North Korean capital, state media said Kim died on a train due to a "great mental and physical strain" on Dec. 17 during a "high intensity field inspection." It said an autopsy was done on Dec. 18 and "fully confirmed" the diagnosis. 
 
 Kim is believed to have suffered a stroke in 2008, but he had appeared relatively vigorous in photos and video from recent trips to China and Russia and in numerous trips around the country carefully documented by state media. 
 
 "It is the biggest loss for the party ... and it is our people and nation's biggest sadness," an anchorwoman clad in black Korean traditional dress said in a voice choked with tears. 
 
 Asian stock markets moved lower amid the news, which raises the possibility of increased instability on the divided Korean peninsula. 
 
 South Korea's Kospi index was down 3.9 percent at 1,767.89 and Japan's Nikkei 225 index fell 0.8 percent to 8,331.00. Hong Kong's Hang Seng slipped 2 percent to 17,929.66 and the Shanghai Composite Index dropped 2 percent to 2,178.75. 
 
 A South Korean Foreign Ministry official, speaking on the condition of anonymity because the ministry was debating ways to respond to Kim's death, said diplomats are shocked but are trying to assess the situation as best as they can. 
 
 Chae Jae-eun, a South Korean company worker, said from Seoul that she worried mostly about the economic implications Kim Jong Il's death would cause. She also said North Korea now stands at a crossroads as the country may isolate itself further or open up. 
 
 Lee Kyu-yun, a parliamentary official, said he is personally scared but refrained from speculating on future developments. He said he was considering stocking up on food in case military tension soars. 
 
 A group of North Koreans waiting at Beijing airport for their flight to Pyongyang reacted with shock when asked of Kim's death. One woman broke into tears as she pulled out a handkerchief. One of her companions led her away when she looked as if she would collapse. 
 
 Another man muttered, "I can't believe it. I can't believe it. This can't be true. We were at the embassy this morning and surely they would have known about this news." 
 
 He composed himself and said I won't believe it until I hear it from my own state media. 
 
 Traffic in the North Korean capital was moving as usual Monday. A foreigner contacted at Pyongyang's Koryo Hotel said hotel staff were in tears. 
 
 ___ 
 
 Associated Press writers Foster Klug, Hyung-jin Kim, Sam Kim and Jiyoung Won contributed to this story from Seoul.
– With the "Dear Leader" dead, North Koreans are being urged to follow the "Respectable Comrade"—Kim Jong Il's third son, who was unveiled as his successor last year. A broadcast on state-run media said the country's people "must faithfully revere respectable comrade Kim Jong Un," the AP reports. "At the leadership of comrade Kim Jong Un, we have to change sadness to strength and courage and overcome today's difficulties." Little is known about the Swiss-educated younger Kim, who is believed to be around 28 years old, but there have already been songs and poems composed to hail his virtues as a leader, the BBC reports. Some 10 million portraits of the young man have reportedly been prepared for distribution to hang alongside those of his father and grandfather in North Korean homes and workplaces. Analysts, however, suspect that the real power in post-Kim Jong Il North Korea will be held by Chang Song Taek, the influential husband of the late leader's sister.