The emergence of China as an economic superpower

There were several conflicting reports on the size of the blast in the northeast North Korea.

The head of South Korea's spy agency told lawmakers that the blast was equivalent to 550 tons of TNT, it was relatively small.

China and France said the explosion measured about half a kiloton (about 500 tons TNT), but they did not confirm it was caused by a nuclear device.

The U.S. Geological Survey said it recorded a seismic event with a preliminary magnitude of 4.2 in northeastern North Korea coinciding with the test, but survey official said the agency was unable to tell if it was an atomic explosion or not.

But, Russia said the blast was a nuclear explosion, and the force of the blast was between five and 15 kilotons, as powerful as the nuclear bombs the U.S. dropped on Japan during World War II. "We have no doubt that it was a nuclear explosion," Russia's Defense Minister Sergei Ivanov said in televised remarks.

So, only Russia said the test was a nuclear explosion.