TOKYO (Reuters) - North Korea appears to have conducted another nuclear test, Japanese national broadcaster NHK said on Wednesday.

Japanese government sources had information that there was a tremor in North Korea this morning and they were checking on the possibility of a nuclear test, NHK said.

Defying warnings from its neighbors, the United States and the U.N. Security Council, North Korea announced on Monday that it had conducted its first-ever nuclear test. Pyongyang had earlier said a U.S. "threat of nuclear war and sanctions" had forced its hand.