The North Korean Central News Agency says North Korea successfully conducted an underground nuclear weapons test Monday morning and that it was conducted safely without radioactive leakage.

But there has been no independent confirmation of the test. A South Korean government official says Seoul is trying to confirm the report.

Presidential spokesman Yoon Tae-young said the Korea Institute of Geoscience and Mineral Resources reported to President Roh Moo-hyun that it detected a strong seismic tremor near the North Korean county of Hwadae, North Hamgyeong Province around 10:35 a.m. The tremor had a magnitude of around three-point-five-seven.

The president called an emergency meeting of top security officials after receiving the report.

The meeting includes Foreign Minister Ban Ki-moon, Unification Minister Lee Jong-seok, Defense Minister Yoon Kwang-ung and presidential security adviser Song Min-soon.

The spokesman said the government is exchanging information with countries concerned and discussing follow-up measures.