NORTH Korea has successfully launched a rocket, boosting the credentials of its new leader and stepping up the threat the isolated and impoverished state poses to opponents.

The rocket, which North Korea says put a weather satellite into orbit, has been labelled by the United States, South Korea and Japan as a test of technology that could one day deliver a nuclear warhead capable of hitting targets as far away as the continental US.

"The satellite has entered the planned orbit," a North Korean television news reader announced, after which the station played patriotic songs with the lyrics "Chosun (Korea) does what it says".

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The rocket was launched just before 10am, according to defence officials in South Korea and Japan, and was more successful than a rocket launched in April that flew for less than two minutes.

The North American Aerospace Defence Command said the rocket "deployed an object that appeared to achieve orbit", the first time an independent body has verified North Korean claims.

The US condemned the launch as "provocative" and a breach of UN rules, while Japan's UN envoy called for a Security Council meeting. However, diplomats say further tough sanctions are unlikely from the Security Council as China, the North's only major ally, will oppose them.

"The international community must work in a concerted fashion to send North Korea a clear message its violations of UN Security Council resolutions have consequences," the White House said in a statement.

US intelligence has linked North Korea with missile shipments to Iran. Newspapers in Japan and South Korea have reported that Iranian observers were in the North for the launch, something Iran has denied.

Japan's likely next prime minister, Shinzo Abe, who is leading in opinion polls ahead of an election on Sunday and who is known as a hawk on North Korea, called on the UN to adopt a resolution "strongly criticising" Pyongyang.

Foreign Secretary William Hague condemned the launch, which he said would increase tensions in the region. Mr Hague said it was a "clear violation" of UN Security Council resolutions because it involved the testing of ballistic missile technology.

A North Korean Foreign Ministry spokesman reiterated the rocket was a "peaceful project". "The attempt to see our satellite launch as a long-range missile launch for military purposes comes from hostile perception that tries to designate us as a cause for security tension," the Korean Central News Agency cited the spokesman as saying.

China had expressed "deep concern" prior to the launch which was announced a day after a top politburo member, representing new Chinese leader Xi Jinping, met Kim Jong-un in Pyongyang.

Yesterday, its tone was measured, regretting the launch but calling for restraint on any counter-measures, in line with a policy of effectively vetoing tougher sanctions.

Bruce Klingner, a Korea expert at the Heritage Foundation, said: "China has been the stumbling block to firmer UN action and we'll have to see if the new leadership is any different."

A senior adviser to South Korea's president said last week it was unlikely there would be action from the UN and Seoul would expect its allies to tighten sanctions unilaterally.

North Korean leader Kim Jong-un, believed to be 29 years old, took power when his father died on December 17 last year and experts believe the launch was intended to commemorate the first anniversary of his death. The April launch was timed for the centennial of the birth of Kim Il Sung.

The North is believed to be some years away from developing a functioning nuclear warhead although it may have enough plutonium for about half-a-dozen nuclear bombs, according to nuclear experts. It has also been enriching uranium, which would give it a second path to nuclear weapons as it sits on big natural uranium reserves.

"A successful launch puts North Korea closer to the capability to deploy a weaponised missile," said Denny Roy, a senior fellow at the East-West Centre in Hawaii.

"But this would still require fitting a weapon to the missile and ensuring a reasonable degree of accuracy. The North Koreans probably do not yet have a nuclear weapon small enough for a missile to carry."