PRAGUE- UNITED States President Barack Obama on Sunday led global condemnation of North Korea's rocket launch, calling it 'a provocative act' for which Pyongyang must be punished.

He was referring to an emergency session of the United National Security Council scheduled to take place in New York today.

Mr Obama was awoken by an aide and told of the news, which occurred in the early morning hours in Prague.

'North Korea broke the rules once more by testing a rocket that could be used for a long-range missile,' he said. 'Rules must be binding. Violations must be punished. Words must mean something. The world must stand together to prevent the spread of these weapons.'

The President added: 'Now is the time for a strong international response. North Korea must know that the path to security and respect will never come through threats and illegal weapons.'

In a speech driven with new urgency by North Korea's rocket launch just hours earlier, Mr Obama said the US would 'immediately and aggressively' seek ratification of a comprehensive ban on testing nuclear weapons.

He outlined ratification of the Comprehensive Test Ban Treaty as one of several 'concrete steps' needed to move towards a nuclear-free world.

The treaty was signed by former president Bill Clinton, but rejected by the Senate in 1999. Over 140 nations have ratified the ban, but 44 states that possess nuclear technology need to both sign and ratify it before it can take effect. Only 35 have done so.

The US is among the key holdouts, along with China, Egypt, India, Indonesia, Iran, Israel, North Korea and Pakistan.

Mr Obama said the US would host a summit within the next year on reducing and eventually eliminating nuclear weapons, and he called for a global effort to secure nuclear material.

More than 20,000 people had gathered in an old square outside the Prague Castle gates for the only open-air address of his European tour. -- AP, AFP