The Secretary-General is confident that the Security Council will remain united and take appropriate action. In the meantime, the Secretary-General remains in close contact with all concerned parties and stands ready to assist their efforts."

Yukiya Amano, International Atomic Energy Agency director general:

"This is deeply regrettable and is in clear violation of U.N. Security Council resolutions."

"The IAEA remains ready to contribute to the peaceful resolution of the DPRK nuclear issue by resuming its nuclear verification activities in the country as soon as the political agreement is reached among countries concerned."

Statement from NATO:

"We condemn in the strongest terms the test by North Korea of a nuclear weapon, conducted in flagrant violation of relevant United Nations Security Council resolutions.

This irresponsible act, along with the December missile launch, poses a grave threat to international and regional peace, security and stability. North Korea's pursuit of weapons of mass destruction represents continued defiance of the U.N. Security Council and the broader international community."

William Hague, British foreign secretary:

"I strongly condemn this development, which is a violation of U.N. Security Council Resolutions 1718, 1874 and 2087. North Korea's development of its nuclear and ballistic missile capabilities poses a threat to international and regional security. Its repeated provocations only serve to increase regional tension, and hinder the prospects for lasting peace on the Korean Peninsula."

Francois Hollande, French president:

"I condemn in the strongest terms the nuclear test just made by North Korea," Hollande said on the French government's website.

"France again urges North Korea to immediately comply with its international obligations and to carry out complete, verifiable and irreversible dismantling of its nuclear and missile programs."

Statement from the German Foreign Office:

Foreign Minister Guido Westerwelle "strongly condemns" North Korea's nuclear test. The "international community should consider further sanctions against the regime," the agency's official Twitter feed said.

Bob Carr, Australian foreign affairs minister:

"The Australian government condemns in the strongest possible terms nuclear testing by North Korea.

"Nuclear testing by North Korea clearly violates United Nations Security Council resolutions ... which demand North Korea not conduct any further nuclear tests.

"North Korea's development of nuclear weapons and missiles and its proliferation of sensitive technologies threaten international peace and security."