By Mark Bendeich
(Reuters) - North Korea's neighbors and its old enemy, the United States, appealed for stability on Monday after the death of the totalitarian state's leader, Kim Jong-il, plunged one of the world's most heavily militarized regions into fresh uncertainty.
Kim suffered a heart attack while travelling on a train, North Korean state media said, setting up the autocratic, well-armed and nuclear-ambitious state for only its second leadership change since the Korean war ended in an uneasy truce in 1953.
Later, state media anointed his youngest son, Kim Jung-un, as the "great successor", but little is known about how he would run a reclusive state with more than a million troops and missiles that Washington fears could one day reach U.S. shores.
President Barack Obama and South Korean and Japanese leaders held telephone hook-ups to discuss the situation, which was unfolding well into Washington's night, while the North's biggest ally, China, expressed grief over Kim's sudden death .
South Korea, still technically at war with the North, put its military on alert after the news, Yonhap news agency said, and President Lee Myung-bak convened its National Security Council. But Seoul's Defense Ministry said there were no signs of any unusual North Korean troop movements.
The White House released a short statement committing itself to working with both South Korea and Japan, two of its closest Asian allies, to ensure continued stability in the region.
"We remain committed to stability on the Korean peninsula, and to the freedom and security of our allies," White House press secretary Jay Carney said in a short written statement.
Japan also convened a special security meeting but stopped short of putting its own armed forces on special alert, and said it had to be prepared for unexpected security developments.
"Prime Minister (Yoshihiko) Noda instructed ministers at the security meeting to prepare for the unexpected, including financial matters, North Korea's domestic issues and border affairs," Japan's top government spokesman said on Monday.
JAPAN NERVOUS OVER MISSILES
Japan is acutely sensitive to uncertainty on the Korean peninsula, after Pyongyang has repeatedly tested missiles into the sea between them and also at times over Japan itself. North Korea has also abducted Japanese citizens.
Asked whether the issue of North Korean missiles had been discussed at the Tokyo security meeting, the government spokesman added: "There was some report on the missile issue at the security meeting but I decline to elaborate."
There was initially a yawning four-hour silence from North Korea's main ally, China, before it praised Kim Jong-il as a great leader who had
made important contributions to relations with
Beijing, a friendship that had helped to maintain stability.
"China and North Korea will strive together to continue making positive contributions to consolidating and developing the traditional friendship between our two parties, governments and peoples, and to preserving the peace and stability of the Korean peninsula and the region , "
state news agency Xinhua quoted Foreign Ministry spokesman Ma Zhaoxu as saying .
Without China's support, many experts believe the Kim dynasty would collapse. Russia, another neighbor with a stake in a stable Korea, had yet to comment on the news.
China, Russia, the United States, Japan, South Korea and North Korea make up the so-called "six-party talks", a troubled dialogue aimed at persuading Pyongyang to scrap nuclear programs and give up ambitions to develop nuclear weapons.
The talks collapsed in 2008, though there have been some fruitless diplomatic efforts since then to revive them.
Taiwan set up an emergency committee
within its Foreign Ministry to monitor
developments on the Korean peninsula and is asking Taiwanese in South Korea to stay alert .
Australia, which fought for the South in the Korean war and maintains diplomatic relations with Pyongyang, called for calm and restraint after Kim Jong-il's death, especially around the so-called demilitarized zone separating the two Koreas.
"It's at times like this that we cannot afford to have any wrong or ambiguous signaling," said Foreign Minister Kevin Rudd, who visited the heavily fortified border zone last month.
"This is the single largest militarily armed zone anywhere in the world and we need to ensure that calm and restraint are exercised in an exceptionally difficult period of transition."
(Writing by Mark Bendeich; Editing by Ed Davies and Robert Birsel)