Updated 5pm: North Korea claims it has successfully launched a satellite into orbit, nine minutes after it was launched this afternoon.

The claim hasn't been verified by South Korea, the United States or Japan.

The New Zealand Government has condemned today's long-range rocket launch by North Korea.

Foreign Minister Murray McCully said it contravenes the UN Security Council resolutions demanding North Korea cease any launches using ballistic missile technology.

He said while North Korea has claimed it as a satellite launch, it may actually be a long-range missile.

Mr McCully said New Zealand will work with other Security Council members to formulate a response.

The United States has also condemned the action.

South Korea's defence ministry announced North Korea had launched a long-range rocket today.

The launch defies United Nations sanctions barring it from using ballistic missile technology.

North Korea had notified UN agencies that it planned to launch a rocket carrying an Earth observation satellite, triggering opposition from governments that see it as a long-range missile test.

Media reports from Japan and South Korea sid the rocket passed over Japan's southern Okinawa islands and appears to have successfully separated its first stage booster.

Japanese Prime Minister Shinzo Abe called the launch "absolutely unacceptable".

Last month, North Korea tested a nuclear device for the fourth time, although the United States and other governments have expressed doubt over the North's claim that it exploded a hydrogen bomb.

North Korea is believed to be working on miniaturising a nuclear warhead to mount on a missile, but many experts say it is some time away from perfecting such technology.

It has shown off two versions of a ballistic missile resembling a type that could reach the US West Coast, but there is no evidence the missiles have been tested.

Isolated North Korea says it has a sovereign right to pursue a space program but it is barred under UN Security Council resolutions from using ballistic missile technology.

It last launched a long-range rocket in December 2012, sending into orbit an object it described as a communications satellite.