North Korea has declared a period of national mourning following the death of leader Kim Jong-il, who died at the age of 69 after suffering a heart attack, North Korean state media announced.
Kim, known in the communist country as the "Dear Leader", died on Saturday aboard a train during a trip out of Pyongyang, the state-run KCNA news agency said on Monday.
"Obviously there will be a long period of public mourning in the country, but the sense is that at least he organised his succession with [his son] Kim Jong-un taking over."
- Don Kirk, Christian Science Monitor
"It is the biggest loss for the party ... and it is our people and nation's biggest sadness," a tearful presenter said as she announced the death on state television.
The presenter also urged the country, people and military to "faithfully revere respectable comrade Kim Jong-un" - Kim's third son and apparent heir.
"At the leadership of comrade Kim Jong-un, we have to change sadness to strength and courage and overcome today's difficulties," she said.
Kim Jong-il last year appointed Kim Jong-un to a number of high-ranking posts in moves seen as positioning him as his assumed successor after years of speculation about the elder Kim's fading health.
Footage broadcast on CCTV, China's main news agency, showed interviews with North Koreans barely able to contain their grief, while the tightly government-controlled KCNA described the entire nation as being in "indescribable sorrow".
"I can't believe it. How can he go like this? What are we supposed to do?" one woman in Pyongyang was quoted as saying.
The announcement of Kim's death prompted South Korea to place its military on emergency alert, while shares on the stock market in Seoul fell amid uncertainty over the stability of the secretive nuclear-armed nation.
North Korea was later reported to have test-fired a short-range missile off its east coast, according to South Korea's Yonhap news agency.
China, considered North Korea's closest ally, said it was shocked to learn of Kim's death.
"We hereby express our deep condolences on his demise and send sincere regards to the North Korean people," a foreign ministry spokesman said.
A White House spokesman said it was closely monitoring reports of Kim's death, while Russia said it expected that Kim's death would not affect "friendly relations" between Moscow and Pyongyang.
Reclusive 'Dear Leader'
Kim was believed to have suffered a stroke in 2008 but 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.
But the leader, reputed to have had a taste for cigars, cognac and gourmet cuisine, was believed to have had diabetes and heart disease.
"Just a couple of days ago, it was publicised that he was visiting a military installation," Don Kirk of the Christian Science Monitor told Al Jazeera.
"Obviously there will be a long period of public mourning in the country, but the sense is that at least he organised his succession with [his son] Kim Jong-un taking over," he said.
An autopsy was performed on Sunday, and the North said the period of national mourning would be in effect from December 17 to 29. KCNA said that Kim's funeral would take place on December 28.
'Axis of evil'
Kim took power in 1994 upon the death of his father, Kim Il-sung, who had led North Korea since the Korean peninsula was split in half by the Korean War. Although the two sides signed a ceasefire in 1953 they remain technically at war.
While Kim Il-sung retained the title of "Eternal President", Kim took the posts of chairman of the national defence commission, commander of the Korean People's Army and head of the ruling Worker's Party.
He continued his father's policy of "military first", devoting much of the country's scarce resources to its troops and building the world's fifth largest military even as many of his country's 23 million population suffered from a prolonged famine.
Kim also sought to develop the country's nuclear arms arsenal, which culminated in North Korea's first nuclear test explosion, an underground blast conducted in October 2006. Another test followed in 2009.
Alarmed, regional leaders negotiated a disarmament-for-aid pact that the North signed in 2007 and began implementing later that year. However, the process continues to be stalled, even as diplomats work to restart negotiations.
North Korea, long hampered by sanctions and unable to feed its own people, is desperate for aid.
Flooding in the 1990s that destroyed the largely mountainous country's arable land left millions hungry.
Following the famine, the number of North Koreans fleeing the country through China rose dramatically, with many telling tales of hunger, political persecution and rights abuses that officials in Pyongyang emphatically denied.
Kim often blamed the US for his country's troubles and his regime routinely derides Washington-allied South Korea as a "puppet" of the Western superpower.
George W Bush, the former US president, in 2002 denounced North Korea as a member of an "axis of evil" that also included Iran and Iraq. He later described Kim as a "tyrant" who starved his people so he could build nuclear weapons.