Residents of North Korea are mourning the death of their "dear leader", Kim Jong-il, after the 69-year-old suffered a heart attack on a train at the weekend.

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The news was announced on state television by a newsreader dressed in black and holding back tears, who said that "great mental and physical strain" had led to his heart attack on Saturday 17 December.

Crowds of people have been wailing and crying on the streets of Pyongyang, to mourn their former leader.

Kim Jong-il suffered a stroke in 2008 and had not been seen in public for months. His youngest son Kim Jong-un was appointed to senior political and military posts in 2010 and is expected to take over from his father.

Kim headed a secretive state with a robust nuclear arms programme and an arsenal of missiles designed for Japan and South Korea, which gained him few international allies.

Read John Sparks: Tears and fears - the death of Kim Jong-il

World leaders are now monitoring how North Korea will react. South Korea has put its military on alert and the neighbouring Japanese prime minister, Yoshihiko Noda, has set up a crisis management team following the news.

Despite his demi-god status in his own country, the former leader presided over an economic crisis that left many of the country's citizens in poverty. Not long after he came to power in 1994, 2 million people died from starvation as a result of his economic strategy and poor harvests.

Asian shares fell following the news, in anticipation of uncertainty surrounding the transition of leadership in North Korea.

The North Korean flag has been lowered to half mast at the country's embassy in Beijing in China - one of the country's rare allies.

North Korea's state-run news agency, KCNA, said: "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."

Read more: A changing North Korea awaits Kim Jong-un
Dear leader's 'supernatural' birth

Kim Jong-il was known for his innumerable eccentricities, writes Inigo Gilmore, with an image fashioned by state-sponsored myths.

Among them were: North Korean schools taught children that his birth was "supernatural". They were told he was born in a log cabin inside a secret base on a sacred mountain, and his arrival was accompanied by the apparition of a new star. Apparently a double rainbow appeared, followed by a talking iceberg.

Western experts, though, say he was born in a guerilla camp in Russia.

North Korean state TV would always repeat the mantra that the "dear leader" was giving invaluable "on the spot guidance" during his interminable visits to construction sites, turkey farms and radish producers.

Kim Jong-un, his youngest son, has clearly been groomed for some time. He has appeared in public with his father, including a high-profile visit to China in May. The chubby-faced son is believed to have been educated partly in Switzerland, and was born in either 1983 or 1984. He is apparently a big fan of basketball.

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