North Korea gave the United States advance notice of its nuclear test on Monday, a South Korean presidential aide said. North Korea's state media said the country successfully conducted a nuclear test on Monday, despite sanctions imposed by the UN Security Council over earlier missile and nuclear tests.

"There was advance notice to the United States," a presidential Blue House official said by telephone. He could not say whether Washington passed on the information to its allies in the region or whether Pyongyang had advised any other governments.