North Korea claims ‘successful’ nuclear test

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.

The official Korean Central News Agency said Tuesday 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 banning Pyongyang from conducting nuclear or missile tests.

Diplomats say the U.N. Security Council will meet early Tuesday in New York to discuss the developments.

South Korea’s Defense Ministry, which has raised its military alert level, also confirmed that an atomic device was exploded Tuesday near the site of Pyongyang’s previous tests.

VOA correspondent Steve Herman in Tokyo says Seoul is also watching for additional explosions or missile launches.

“There’s also concern that North Korea, at the same time that it was doing this nuclear test, or on the same day, might also launch some medium-range missiles, (but) we’ve had no confirmation of any such activity so far,” he said. “This is being taken very seriously by North Korea’s neighbors, especially South Korea and Japan.”

North Korea had threatened to carry out its third nuclear test in retaliation for United Nations sanctions that were expanded last month in response to a recent long-range rocket launch.

Initial reports suggested that North Korea’s latest nuclear test was stronger than its previous tests in 2006 and 2009. A North Korea Defense Ministry spokesperson said the explosion generated 6-7 kilotons of nuclear energy. But South Korean officials are still investigating whether the latest test used plutonium, as in previous tests, or uranium.

North Korea is believed to have enough plutonium to make several weapons. In 2009, Pyongyang announced it also would begin enriching uranium, giving it a second way to make fuel for nuclear weapons.

Earlier Tuesday, North Korean state media threatened an unspecified “high-intensity” action, but did not mention any possible nuclear test. Last month, Pyongyang threatened to continue nuclear and missile tests it said were aimed at the  United States.

Since then, there had been much speculation about the timing of the possible test. South Korean officials told various media outlets that North Korea informed the U.S. and China of the impending test.

China, North Korea’s only major ally and an important source of economic aid, agreed to the Security Council sanctions last month, and has expressed unusual criticism of North Korea’s nuclear program.

The Comprehensive Nuclear Test Ban Treaty, an international monitoring group, says the test “would constitute a a clear threat to international peace and security.”