South Korea's weather agency said a magnitude 3.0 earthquake was detected in North Korea on Saturday around where the country recently conducted a nuclear test, but it assessed the quake as natural.

The quake was detected in an area around Kilju, in northeastern North Korea, and about 12 miles southeast of where the North conducted its sixth and most powerful nuclear test on September 3, according to an official from Seoul's Korea Meteorological Administration.

China's official Xinhua News Agency said earlier that the country's seismic service detected a magnitude 3.4 quake in North Korea and saw the likely cause as an explosion.

But the official from the South Korean agency said the analysis of seismic waves and the lack of sound waves clearly showed that the quake wasn't caused by an artificial explosion. She spoke on condition of anonymity, citing office rules.