South Korean warships fanned out across the Yellow Sea today to search for debris from North Korea's failed rocket launch, which brought humiliation for the country's new young leader and condemnation from a host of nations.

The rocket's disintegration just moments after lift-off yesterday brought a rare public acknowledgment of failure from Pyongyang, which had hailed the launch as a show of strength amid North Korea's persistent economic hardship.

The UN Security Council deplored the launch but stopped short of imposing new penalties in response.

For the 20-something Kim Jong Un it was to have been a highlight of the celebratory events surrounding his ascension to top political power. It was timed to coincide with the country's biggest holiday in decades - the 100th birthday of North Korean founder Kim Il Sung, the young leader's grandfather.

The United States and South Korea declared the early-morning launch a failure minutes after the rocket shot out from the North's west coast.

North Korea acknowledged its demise four hours later in an announcement broadcast on state TV, saying the satellite the rocket was carrying did not enter orbit.

The launch brought swift international condemnation, including the suspension of US food aid, and raised concerns that the North's next move could be even more provocative - a nuclear test, the country's third.

The UN Security Council denounced the launch as a violation of two resolutions that prohibit North Korea from developing its nuclear and missile programmes, and met behind closed doors to consider a response. The council imposed sanctions on North Korea after its first nuclear test in 2006 and stepped up sanctions after its second in 2009.

US President Barack Obama said North Korea's failed rocket launch shows the country is wasting money on rockets that "don't work" while its people starve.

He told Spanish-language TV network Telemundo that the North Koreans have "been trying to launch missiles like this for over a decade now, and they don't seem to be real good at it".

Despite yesterday's failed launch, Pyongyang pressed ahead with grandiose propaganda in praise of the ruling Kim family.

Hours after the explosion, the young Kim was installed as the new head of the powerful National Defence Commission during a meeting of the Supreme People's Assembly in Pyongyang. It was the last of the top military and party posts intended to consolidate his power after the death of his father, long-time leader Kim Jong Il, four months ago.

At a massive gathering later, Kim Jong Un and other senior officials watched the unveiling of an enormous new statue of Kim Jong Il, which stood beside an equally massive one of Kim Il Sung.

Today, the North's official media announced that Kim Jong Un has promoted dozens of general-grade officers to mark the centennial of the birth of his grandfather.

The military's top political officer, Choe Ryong Hae, was also elected a member of the National Defence Commission in the latest reshuffle meant to tighten Kim's grip on power, the Korean Central News Agency said.

North Korea had trumpeted the launch of its Kwangmyongsong, or Bright Shining Star, satellite as a scientific achievement. It cost the impoverished nation some 850 million US dollars (£534 million), according to South Korea's Yonhap news agency, which estimated the cost of the rocket and its payload alone at 450 million dollars (£282.7 million).

The rocket's destruction suggests the country has yet to master the technology needed to build long-range missiles that could threaten the United States. Nevertheless, worries remain about North Korea's nuclear programme amid reports that it may be planning an atomic test soon.

The launch was condemned by the foreign ministers of the Group of Eight industrialised nations meeting in Washington, including Russia, while Washington said it was suspending plans to contribute food aid to the North in exchange for a rollback of its nuclear programmes.

North Korea announced weeks ago that it would launch a long-range rocket mounted with an observational satellite to mark the centennial of Kim Il Sung's birth.

Experts say the Unha-3 carrier was the same type of rocket that would be used to strike the US and other targets with a long-range missile.

The Unha-3's launch was monitored by US, Japanese and South Korean military assets, which were expected to capture vital data on North Korea's ballistic missile capabilities.

South Korea's Navy has deployed about 10 ships, including a corvette with sonar radars, to search for rocket debris in the Yellow Sea, a Defence Ministry official said today.

He would not comment on local media reports that a destroyer is leading the search effort.

US Navy minesweepers and other ships in the area were expected to begin scouring the sea for debris from the rocket, which can offer evidence of what went wrong and what rocket technology North Korea has.

Greg Thielmann, a former intelligence officer with the US State Department, said it appears the North Koreans have not mastered the technology they need to control multi-stage rockets - a key capability if the North is to threaten the United States with intercontinental ballistic missiles.

North Korea has tested two atomic devices but is not yet believed to be able to build a nuclear warhead small enough to be mounted on a long-range missile.

Meanwhile, state media acknowledged that the satellite "failed to enter its preset orbit".

"Scientists, technicians and experts are now looking into the cause of the failure," KCNA said.

The acknowledgment of the rocket's failure - both to the outside world and to North Koreans - was a surprising admission by a government that in the past has kept tight control over information.