The UN Security Council has unanimously condemned North Korea's latest nuclear test.
A council statement said it was a 'clear violation' of a resolution passed in 2006 after Pyongyang's first atomic test.
The statement followed a closed-door council meeting in New York.
It added that the members of the Council had decided to start work immediately on a Security Council resolution on the matter.
There has been widespread condemnation of North Korea after it announced it had carried out a second underground nuclear test.
European leaders earlier called for a strong international response to North Korea's nuclear bomb test.
They condemned the ‘cynical game’ by a nation they described as struggling to feed its people.
European Commission President Jose Manuel Barroso called the bomb test a ‘provocation’ and urged the international community to clearly reject the move.
British Prime Minister Gordon Brown called North Korea 'a danger to the world', and Russia said the test was about equal in power to the US atom bomb dropped on Nagasaki.
Meanwhile, US President Barack Obama said the international community must act after North Korea's ‘reckless’ nuclear and missile tests.
‘The United States and the international community must take action in response,’ he said.
‘North Korea's nuclear ballistic missile programs pose a grave threat to the peace and security of the world and I strongly condemn their reckless actions,’ he said.
North Korea's official news agency said the test it carried out was on a higher level, in terms of its explosive power and technology,
than the first test three years ago.
South Korea responded by putting its troops on a state of heightened alert.
The alarm was raised by seismologists who detected an event of magnitude 4.7 centred on the north eastern region of North Korea.
