North Korea says it has "successfully" carried out a third nuclear test, in defiance of U.N. warnings to stop developing its atomic weapons program.
State media Tuesday said the underground test used a "lighter, miniaturized nuclear bomb" with greater explosive force than previous tests. It said the test was in response to what it called the "reckless hostility" of the United States.
U.N. Secretary General Ban Ki-moon immediately condemned the "deeply destabilizing" move, calling it a "clear and grave violation" of international sanctions.
U.S. President Barack Obama called the test "highly provocative," saying it threatens U.S. security and international peace. He called for "swift and credible" action by the international community.
China, North Korea's main ally, expressed what it called "firm opposition" to the test.
Diplomats say the U.N. Security Council will meet early Tuesday in New York to come up with a response.