NYT:

North Korea announced on Monday that it had successfully conducted its second nuclear test, defying international warnings and dramatically raising the stakes in a global effort to persuade the recalcitrant Communist state to give up its weapons program. ...

Russia and Japan said the U.N. Security Council would hold an emergency meeting Monday.

Geological authorities in the United States, Japan and South Korea reported that the test triggered an earth tremor with a magnitude of between 4.5 and 5.3. The tremor emanated from Kilju, the same area where the North Korea carried out a test in October 2006.