North Korea says it conducted successful underground nuclear weapons test

SEOUL, South Korea — North Korea said today it has performed its first-ever nuclear weapons test, setting off an underground blast in defiance of international warnings and intense diplomatic activity aimed at heading off such a move.

The North Korean statement said there was no radioactive leakage from the test site.

An official at South Korea's seismic monitoring center confirmed a magnitude-3.6 tremor felt at the time North Korea said it conducted the test was not a natural occurrence. The official spoke to The Associated Press on condition his name not be used, because he was not authorized to talk about the sensitive information to the media.

Japanese Prime Minister Shinzo Abe said that information still needs to collected and analyzed to determine whether North Korea truly conducted its first nuclear test.

U.S. and South Korean officials could not immediately confirm the report.

South Korea's Defense Ministry said the alert level of the military had been raised in response to the claimed nuclear test.

The North said last week it would conduct a test, sparking regional concern and frantic diplomatic efforts aimed at dissuading Pyongyang from such a move. North Korea has long claimed to have nuclear weapons, but had never before performed a known test to prove its arsenal.

The North's official Korean Central News Agency said the underground test was performed successfully.

"It marks a historic event as it greatly encouraged and pleased the ... people that have wished to have powerful self-reliant defense capability," the KCNA statement said.

"It will contribute to defending the peace and stability on the Korean Peninsula and in the area around it."

South Korean intelligence officials said the seismic wave had been detected in North Hamkyung province, according to South Korea's Yonhap news agency. It said the test was conducted at 10:36 a.m. (9:36 p.m. EDT Sunday) in Hwaderi near Kilju city on the northeast coast, citing defense officials.

North Korean scientists "successfully conducted an underground nuclear test under secure conditions," the KCNA report said, adding this was "a stirring time when all the people of the country are making a great leap forward in the building of a great prosperous powerful socialist nation."