North Korean leader Kim Jong Il is dead, state television in Pyongyang has announced.
Kim, who was known as the "dear leader" by his people, reportedly died "from great mental and physical strain" on a train on Saturday 17 December.
Power in the nuclear-armed state is now expected to transfer to Kim's son Kim Jong-un, who is believed to be in his late 20s or early 30s and was named as successor before his father's death.
"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 Korean Central News Agency (KCNA) said.
Meanwhile it was reported by the Reuters news agency that North Korea had test-fired a short-range missile on Monday morning.
KCNA added in a release titled 'Medical Analysis of Kim Jong Il's demise' that Kim suffered an "advanced acute myocardial infarction, complicated with a serious heart shock."
The leader, who took power in 1994 after the death of his father Kim Il-Sung, was reported to have suffered a stroke in 2008. However he had appeared relatively healthy on recent trips around Asia, despite reports he may have been suffering from cancer.
Kim's funeral will be held in Pyongyang on 28 December, and his son will lead the funeral committee state media reported. There will be a period of national mourning from 17 to 29 December.
State media portrayed the reaction inside North Korea as one of deep sadness and shock. News announcers shook and wept as they announced the news.
Other commentators claimed that the wailing and public tears of mourners in the country appeared forced:
However there were reports of gunfire breaking the silence in Pyongyang, after the BBC reported that shots were heard near to the Kumsusan Memorial Palace after Kim's death was revealed.
British Foreign Secretary William Hague said:
"The people of North Korea are in official mourning after the death of Kim Jong Il. We understand this is a difficult time for them. This could be a turning point for North Korea. We hope that their new leadership will recognise that engagement with the international community offers the best prospect of improving the lives of ordinary North Korean people. We encourage North Korea to work for peace and security in the region and take the steps necessary to allow the resumption of the Six Party Talks on denuclearisation of the Korean Peninsula".
China reacted to the news by paying tribute to Kim's leadership:
"We were distressed to learn of the unfortunate passing of the senior-most North Korean leader Kim Jong-il, and we express our grief about this and extend our condolences to the people of North Korea," a foreign ministry spokesman was quoted as saying by the Xinhua state news agency.
The White House said that it was monitoring the situation, and added that President Obama had spoken to South Korea's President Lee-Myung-bak after the news broke.
"We are closely monitoring reports that Kim Jong Il is dead," the White House said. "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."
Outside of North Korea Kim Jong Il will be remembered as a brutal leader who prioritised military growth over his own people's welfare.
Under Kim, North Korea built the world's fifth-largest military - even as the country starved in a prolonged famine. He also relentlessly pursued nuclear ams, an endeavour which culminated in the country's first nuclear test in 2006.
He is also accused by South Korea of being behind a bombing in Myanmar that killed 17 of its officials, and the 1987 bombing of a Korean Air Flight plane that killed 115 people.