North Korea fired a long-range rocket over Japan on Sunday, provoking international condemnation and triggering an emergency meeting of the UN Security Council as it succeeded in grabbing the world's attention.

The reclusive communist state's official media said a satellite had been launched into orbit, and it was now circling the earth transmitting revolutionary songs.

US President Barack Obama said North Korea, which tested a nuclear device in 2006, had violated UN resolutions with what analysts believe was effectively a test of a ballistic missile designed to carry a warhead potentially as far as Alaska.

"With this provocative act, North Korea has ignored its international obligations, rejected unequivocal calls for restraint, and further isolated itself from the community of nations," Obama, who is on a European tour, said in a statement.

In a speech to be delivered in Prague later, Obama will commit himself to reducing the US nuclear arsenal, bringing the Comprehensive Test Ban Treaty into force and seeking tough penalties for nuclear rule-breakers, the White House said.

The White House said that Obama will also say he remains committed to six-nation talks to "denuclearise" North Korea.

South Korea branded the launch of the rocket a "reckless" act, Japan said it was "extremely regrettable" and the European Union "strongly condemned" Pyongyang's step.

China, the nearest the reclusive North has to a major ally, and Russia both called on all sides for calm and restraint.