North Korea said its much hyped long-range rocket launch failed on Friday, in a very rare and embarrassing public admission of failure by the hermit state and a blow for its new young leader who faces international outrage over the attempt.

The isolated North, using the launch to celebrate the 100th birthday of the dead founding president Kim Il-sung and to mark the rise to power of his grandson Kim Jong-un, is now widely expected to press ahead with its third nuclear test to show its military strength.

"The possibility of an additional long-range rocket launch or a nuclear test, as well as a military provocation to strengthen internal solidarity is very high," a senior South Korean defense ministry official told a parliamentary hearing.

The two Koreas are divided by the world's most militarized border and remain technically at war after an armistice ended the Korean War in 1953.

The United States and Japan said the rocket, which they claimed was a disguised missile test and the North said was to put a satellite into orbit, crashed into the sea after traveling a much shorter distance than a previous North Korean launch.

Its failure raises questions over the impoverished North's reclusive leadership which has one of the world's largest standing armies but cannot feed its people without outside aid, largely from its only powerful backer, China.

"(There is) no question that the failed launch turns speculation toward the ramifications for the leadership in Pyongyang: a fireworks display gone bad on the biggest day of the year," said Scott Snyder of the Council on Foreign Relations.

In a highly unusual move, the North, which still claims success with a 2009 satellite that others say failed, admitted in a state television broadcast seen by its 23 million people that the latest satellite had not made it into orbit.

The failure is the first major and very public challenge for the third of the Kim dynasty to rule North Korea just months into the leadership of a man believed to be in his late 20s.

"It could be indication of subtle change in the North Korean leadership in how they handle these things, something that may be different from the past," said Baek Seung-joo of the Korea Institute of Defense Analyses a think tank affiliated with South Korean Defense Ministry.

"I mean it would have been unthinkable for them to admit this kind of failure in the past, something that could be seen as an international humiliation. The decision to have come out with the admission had to come from Kim Jong-un."

Embarrassingly, the rocket flew for just a few minutes covering a little over 100km to explode over a sea separating the Korean peninsula and China, far less than the last rocket in 2009 that traveled 3,800km, alarming Japan, which it over-flew.

The launch is in breach of United Nations Security Council sanctions and drew condemnation from the United States, Russia, South Korea and Japan.

But North Korea looks to have avoided the threat of fresh UN sanctions - which neighbor Japan is pushing for - after Russian Foreign Minister Sergei Lavrov said that at talks with his Chinese and Indian counterparts they had agreed new sanctions would do nothing to help resolve the situation.

Regional powers are worried that the North is using launches to perfect technology to enable it to build a missile capable of delivering a nuclear warhead to the United States.

North Korea has repeatedly defended its right to launch rockets for what it says are peaceful purposes and may have invested hundreds of millions of dollars in the failed launch.

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