A magnitude 3.0 earthquake has been detected in North Korea around where a nuclear test recently took place but it has been assessed as natural, South Korea’s weather agency said.

The earthquake was detected in an area around Kilju, in north-east North Korea.

That is about 20km (12m) south-east of where the North conducted its sixth and most powerful nuclear test on September 3, an official from the Korea Meteorological Administration in Seoul said.

China’s official Xinhua News Agency said earlier that its 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 was not caused by an artificial explosion.

The US Geological Survey (USGS) said that it detected a magnitude 3.5 quake in the area of previous North Korean nuclear tests, but that it was unable to confirm whether the event was natural.

North Korea’s weakest nuclear test, the first one conducted in 2006, generated a magnitude 4.3 quake. The USGS measured this month’s nuclear test at magnitude 6.3.

(AP)(AP)

North Korea has been maintaining a torrid pace in nuclear and weapons tests as it accelerates its pursuit of nuclear weapons that could viably target the United States and its allies in Asia.

North Korea said its recent nuclear test was a detonation of a thermonuclear weapon built for its developmental intercontinental ballistic missiles.

In two July flight tests, those missiles showed potential capability to reach deep into the US mainland when perfected.