North Korea confirmed this morning that it has successfully conducted a third nuclear test, saying it used a miniaturized device that had a greater explosive force than previous tests, the North's KCNA official news agency said.

"It was confirmed that the nuclear test that was carried out at a high level in a safe and perfect manner using a miniaturized and lighter nuclear device with greater explosive force than previously did not pose any negative impact on the surrounding ecological environment," KCNA said.

The United States, Russia and the United Nations Secretary General condemned the test.

Russia called it a violation of Pyonyang's international obligations.

U.N. Secretary-General Ban Ki-moon said it was "deplorable" that Pyongyang had defied international appeals to refrain from such provocative acts.

South Korea said this was a direct challenge to the international community and an unforgivable threat to peace and stability of the Korean peninsula and Northeast Asia.