Space officials had announced they would launch a satellite this week as part of celebrations honouring North Korea founder Kim Il Sung. Lift-off took place at 7:39am from the west coast launch pad in the hamlet of Tongchang-ri, South Korea's Joint Chiefs of Staff in Seoul said.
However, the launch appeared to have failed, with the rocket splintering into pieces moments after take-off, South Korea's Defence Ministry said in Seoul.
"We suspect the North Korean missile has fallen as it divided into pieces minutes after lift-off," Defence Ministry spokesman Kim Min-seok told reporters.
In Washington, a US official also said the launch appeared to have failed.
Tokyo, which was prepared to shoot down any rocket flying over its territory, also confirmed a launch from North Korea.
"We have confirmed that a certain flying object has been launched and fell after flying for just over a minute," Japan's Defence Minister Naoki Tanaka said. He said there was no impact on Japanese territory.
"For all their advanced technology, these rockets are fairly fragile things," said Brian Weeden, a technical adviser at Secure World Foundation who is a former Air Force officer at the US Space Command. "You're looking at a metal cylinder that has fairly thin walls that contains a lot of high pressure liquid."
In Pyongyang, there was no word about a launch, and at the time, state television was broadcasting video of popular folk tunes. North Korean officials said they would make an announcement about the launch "soon."
North Korea had earlier announced it would send a three-stage rocket mounted with a satellite as part of celebrations honouring late President Kim Il Sung, whose 100th birthday is being celebrated Sunday.
A failure would be a huge blow to a nation that has staked its pride on a satellite launch seen as a show of strength amid persistent economic hardship as North Korea's young new leader, Kim Jong Un, solidifies power following the death of his father, longtime leader Kim Jong Il, four months ago.
North Korean space officials said the Unha-3 rocket is meant to send a satellite into orbit to study crops and weather patterns its third bid to launch a satellite since 1998. Officials took foreign journalists to the west coast site to see the rocket and the Kwangmyongsong-3 satellite Sunday in a bid to show its transparency amid accusations of defiance.
The United States, Britain, Japan and others have called such a launch a violation of UN resolutions prohibiting North Korea from nuclear and ballistic missile activity.
Experts say the Unha-3 carrier is the same type of rocket that would be used to launch a long-range missile aimed at the US and other targets. North Korea has tested two atomic devices but is not believed to have mastered the technology needed to mount a nuclear warhead on a long-range missile.
US Secretary of State Hillary Clinton, speaking for the Group of Eight nations after their foreign ministers met in Washington, said on Thursday that all the members of the bloc agreed to be prepared to take further action against North Korea in the Security Council if the launch went ahead.
"Pyongyang has a clear choice: It can pursue peace and reap the benefits of closer ties with the international community, including the United States; or it can continue to face pressure and isolation," Clinton said.
South Korean President Lee Myung-bak was convening an emergency security meeting, officials said.
According to projections, the first stage of the rocket was to fall into the ocean off the western coast of South Korea, while a second stage would fall into waters off the eastern coast of the Philippine island of Luzon.
Weeden said the launch appeared to be a failure of both space and missile objectives.
"The earlier it breaks up, the less data you've collected, so the less useful that test is likely to be," he said. "It's very likely that the US and its allies probably gathered more information about this test than the North Koreans have."
He said US and other nations had been poised to keep close watch on the launch to gather intelligence about the state of North Korea's rocket program.