By Christine Kim and Raju Gopalakrishnan
SEOUL (Reuters) - When South Korean President Lee Myung-bak left on a state visit for Japan last week, North Korean leader Kim Jong-il had been dead for about four hours, indicating that neither Seoul nor Tokyo -- or Washington -- had any inkling of his death.
North Korean state media announced Kim's death two days later, on Monday, apparently catching governments around the world by surprise and plunging the region into uncertainty over the stability of the unpredictable state that is trying to build a nuclear arsenal.
Lee held talks in Tokyo with Prime Minister Yoshihiko Noda and returned home on Sunday afternoon, apparently still unaware of the cover-up by the North, with which South Korea is still technically at war. If Washington had known, it appears likely it would have tipped off South Korea and Japan, its closest allies in Asia.
"It seems everyone learned about Kim Jong-il's death after (the announcement)," said Kim Jin-pyo, head of the intelligence committee for South Korea's parliament after discussions with officials from the National Intelligence Service.
"The U.S., Japan and Russia knew after North Korea's announcement," he told reporters.
South Korea put its troops on emergency alert after the announcement of Kim's death; Japan said it had to be prepared for "unexpected" developments.
South Korea's main spy agency and the defense ministry were completely in the dark until they saw the announcement on television, Yonhap news agency said.
Other countries were similarly caught off-guard.
"We knew he had an increased risk of a coronary event for some time now, but clearly no one can know exactly when something like this will happen," a U.S. official said on condition of anonymity.
"No one was on death watch," said Ralph Cossa, president of the U.S. think tank Pacific Forum CSIS. "If anyone thought they had a good handle on North Korea, the sources were not that good."
Western spy agencies use satellites, electronic eavesdropping and intelligence from Asian allies with greater access to try and deduce what is going on inside the hermetic country.
There is some human intelligence, but obviously it was not up to the task.
"There is all sorts of human intelligence at all sorts of levels in North Korea," said Cossa. "But certainly, the inner circle has not been breached.
"North Korea is very good at keeping secrets, it probably had procedures in place which it was implementing."
When founder Kim Il-sung died in 1994, the state kept it a secret for more than a day.
Some reports say North Korea's solitary ally, China, may have been tipped off about Kim's death, and it did not share that information.
"One would assume China would be the first to be notified," Cossa said. "On the other hand, with North Korea, there is no such thing as a safe assumption."
(Editing by Alex Richardson)