PYONGYANG, North Korea — Kim Jong Il, North Korea's longtime dictator who allowed his people to starve while building a vast military, has died of heart failure. His death sparked immediate concern over who is in control of the reclusive state and its nuclear program.
Citing YTN TV, Reuters also reported that North Korea test-fired a short-range missile off the country's east coast on Monday.
A "special broadcast" from the North Korean capital, state media said the 69-year-old died of a heart ailment on a train due to a "great mental and physical strain" on Saturday during a "high intensity field inspection." It said an autopsy was completed on Sunday and "fully confirmed" the diagnosis.
A spokesperson at the Unification Ministry confirmed Kim's death to NBC News. His funeral will be held on December 28.
Video: What Kim Jong Il's death means for region (on this page)
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.
The communist country's "Dear Leader" — reputed to have had a taste for cigars, cognac and gourmet cuisine — was believed to have had diabetes and heart disease.
"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. She said the nation must "change our sadness to strength and overcome our difficulties."
Mindful of North Korea's nuclear weapons programs and 1.2 million-strong armed forces, South Korea put its military on alert. President Lee Myung-bak also convened a national security council meeting after the news of Kim's death.
Kim Jong Un, Kim's youngest son, was named by North Korea's official news agency KCNA as the "great successor" to his father , which lauded him as "the outstanding leader of our party, army and people."
Video from Chinese state television showed residents of Pyongyang, the North Korean capital, weeping while KCNA reported people were "writhing in pain" from the loss.
President Barack Obama was monitoring reports of the death of the North Korean leader, the White House said Sunday night, adding that U.S. officials were in contact with 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 White House said in a statement.
Video: Even in death, details of Kim Jong Il's life elusive (on this page)
In Japan, the government said in a statement on Monday that Prime Minister Yoshihiko Noda told ministers and officials to boost information gathering on the future of North Korea and to be ready for the unexpected, Reuters reported.
Kim Jong Il inherited power after his father, revered North Korean founder Kim Il Sung, died in 1994. In September 2010, Kim Jong Il introduced his third son, the 20-something Kim Jong Un, as his successor, putting him in high-ranking posts.
Jim Hoare, a British former diplomat who served in North Korea after the countries established relations in 2000, told Sky News that Kim's death left considerable uncertainty.
"Nobody can be sure what change will be like," he said. "We don't really know who has power, who doesn't have power. We're always guessing."
Hoare said that television footage showing emotional North Koreans could be seen as "formalized grief."
"This is what people expect to do on a sad occasion," he added. "Whether they genuinely feel it, I don't know."
Asian stock markets sank Monday amid the news, which raises the possibility of increased instability on the divided Korean peninsula.
Slideshow: Daily life in North Korea (on this page)
South Korea's Kospi index dived 4.1 percent but later recouped some losses to trade 3.4 percent lower at 1,777.64 by early afternoon. The Korean won fell 1.6 percent against the U.S. dollar, a traditional haven in times of uncertainty. The Japanese yen and euro also weakened against the dollar.
Japan's Nikkei 225 index was down 1.1 percent at 8,308.42, Hong Kong's Hang Seng slid 2.2 percent to 17,890.13 and the Shanghai Composite Index fell 1.6 percent to 2,188.39.
Even with a successor, there had been some fear among North Korean observers of a behind-the-scenes power struggle or nuclear instability upon the elder Kim's death.
Few firm facts are available when it comes to North Korea, one of the most isolated countries in the world, and not much is clear about the man known as the "Dear Leader."
Birth heralded by rainbows
North Korean legend has it that Kim was born on Mount Paektu, one of Korea's most cherished sites, in 1942, a birth heralded in the heavens by a pair of rainbows and a brilliant new star. Soviet records, however, indicate he was born in Siberia, in 1941.
Kim Il Sung, who for years fought for independence from Korea's colonial ruler, Japan, from a base in Russia, emerged as a communist leader after returning to Korea in 1945 after Japan was defeated in World War II.
With the peninsula divided between the Soviet-administered north and the U.S.-administered south, Kim rose to power as North Korea's first leader in 1948 while Syngman Rhee became South Korea's first president.
The North invaded the South in 1950, sparking a war that would last three years, kill millions of civilians and leave the peninsula divided by a Demilitarized Zone that today remains one of the world's most heavily fortified. The Korean peninsula remains technically in a state of war more than 50 years after the Cold War-era armed conflict ended in a cease-fire.
In the North, Kim Il Sung meshed Stalinist ideology with a cult of personality that encompassed him and his son. Their portraits hang in every building in North Korea and on the lapels of every dutiful North Korean.
Kim Jong Il, a graduate of Pyongyang's Kim Il Sung University, was 33 when his father anointed him his eventual successor.
Even before he took over as leader, there were signs the younger Kim would maintain — and perhaps exceed — his father's hard-line stance.
South Korea has accused Kim of masterminding a 1983 bombing that killed 17 South Korean officials visiting Burma, now known as Myanmar. In 1987, the bombing of a Korean Air Flight killed all 115 people on board; a North Korean agent who confessed to planting the device said Kim ordered the downing of the plane himself.