SEOUL, South Korea — North Korea today said it has performed its first nuclear weapons test. U.S. and South Korean officials could not immediately confirm the report. The North’s official Korean Central News Agency said the underground test was performed successfully and there was no radioactive leakage from the site.

South Korean intelligence officials said a seismic wave of magnitude-3.58 had been detected in North Hamkyung province, according to Yonhap. Citing defense officials, it said the test was conducted at 10:36 a.m. (9:36 p.m. EDT yesterday) in Hwaderi near Kilju city on the northeast coast.

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.”

The director of South Korea’s monitoring center that is watching for a test with sound and seismic detectors declined to immediately comment on the reported test.

“We don’t know whether it is a nuclear test or not,” an official at the earthquake center at the Korea Institute of Geoscience and Mineral Resources said on condition of anonymity, citing the sensitive nature of the issue.

The U.S. Geological Survey said it had detected no seismic activity in North Korea, although it was not clear whether a blast would be strong enough for its sensors.

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 nuclear test is a historic event that brought happiness to our military and people,” KCNA said. “The nuclear test will contribute to maintaining peace and stability in the Korean peninsula and surrounding region.”

Last night, American government officials said a wide range of agencies were looking into the report of the nuclear test, which officials were taking seriously. South Korea’s president, Roh Moohyun, has convened a meeting of security advisers over the issue, Yonhap reported, and intelligence over the test has been exchanged between concerned countries. Kyodo News agency reported that the Japanese government has set up a taskforce in response to reports of the test. The North has refused for a year to attend international talks aimed at persuading it to disarm. The country pulled out of the Nuclear Nonproliferation Treaty in 2003 after U.S.officials accused it of a secret nuclear program, allegedly violating an earlier nuclear pact between Washington and Pyongyang.