North Korea's Kim Jong-il dies: Regional reaction
BBC correspondents look at how North Korea's neighbours have responded to the death of Kim Jong-il and the impact it may have on the region.
John Sudworth, BBC Seoul correspondent
Following the news of Kim Jong-il's death, South Korea is keeping a careful watch. It can do little else. The military and government departments have been placed on a heightened state of alert.
It is almost certain that North Korea has done the same, faced as it is with a politically fraught transition of power to Kim Jong-il's youngest son, a totally untried and untested heir.
The concern will be that it is in just such an atmosphere that mistakes are made.
North Korea is reported to have test-fired a short-range missile shortly before the announcement of Mr Kim's death this morning. The firing is not in itself unusual, but the timing is being seen by some as a message of sorts from the North Korean military: "We're still in business."
But amid this uncertainty, many South Koreans will be daring to hope that there is an opportunity for change. Kim Jong-il leaves behind a country now so out of step with the outside world, with a basket-case economy and such a pitiful human rights record.
If there are any reform-minded figures inside the North Korean elite, maybe, just maybe, this could be their moment. Do not count on it, of course.
The announcement of Kim Jong-il's death came two full days after the fact. That it was seemingly kept from the prying eyes of numerous intelligence agencies is perhaps an ominous signal - that, for the moment, the secretive, authoritarian status quo is likely to prevail.
Michael Bristow, BBC Beijing correspondent
China is North Korea's chief supporter, so it is perhaps no surprise that it paid lavish praise to Kim Jong-il, who died on Saturday.
Chinese foreign ministry spokesman Ma Zhaoxu described Mr Kim as a "great leader" and a friend.
He said the North Korean leader had made important contributions to the development of socialism in his country.
Mr Ma also sent his condolences to the people of the North.
China and North Korea's friendship dates from the Korean War, when China sent troops to fight with the North.
Former Chinese leader Mao Zedong once said the two neighbours were as close as lips and teeth.
Their relationship has changed since then, as China has opened up to the outside world, while North Korea has stayed much the same.
But China has continued to provide economic and diplomatic support.
Following news of Kim Jong-il's death, the Chinese foreign ministry spokesman said the two countries would continue to protect "peace and stability".
It is an indication that China hopes the close relationship between Beijing and Pyongyang will continue under the North's new leadership.
Roland Buerk, BBC Tokyo correspondent
Japan's government offered condolences to North Korea on the death of Kim Jong-il - but not before ministers had gathered for an emergency security meeting in Tokyo.
Prime Minister Yoshihiko Noda later told reporters he hoped it would not have a negative impact on peace and security on the Korean peninsula.
Chief Cabinet Secretary Osamu Fujimura said: "We need to watch risks related to the succession."
Officials in Japan have been warned to prepare for the unexpected.
The Self Defence Forces and the Coastguard have been ordered to stay vigilant and watchful.
Japan is very aware its great cities are potentially in range.
As recently as 2009, North Korea test-fired what Japan and the US said was a missile that flew right over the country.
Pyongyang said it was putting a satellite in orbit.
Patriot anti-missile batteries had been set up in Tokyo but in the event were not fired in defence of the capital.
Japan has no diplomatic ties with North Korea, but the two countries share a fraught history.
Before 1945 the Korean peninsula was a Japanese colony.
Hundreds of thousands of ethnic Koreans live in Japan, many descendants of people brought into the country as forced labourers.
Some back Pyongyang and send their children to schools in Japan where the portraits of Kim Jong-il and his father Kim Il-sung stare down from the classroom walls.
Tokyo's other big concern as North Korea enters a period of flux is the fate of Japanese citizens abducted by Pyongyang in the 1970s and 1980s to use to train its spies.
The families of some of those taken have said they fear the death of Kim Jong-il might further delay efforts to secure their return.
Others have expressed hopes that a change of leadership in North Korea could produce a breakthrough.