An earthquake measuring 5.9 on the Richter scale struck off the coast of North Korea on Thursday morning, the US Geological Survey (USGS) said.

According to the USGS, the earthquake occurred at 4.18 a.m. (local time), 180 km off the northeastern coast of North Korea, close to where the Punggye-ri nuclear test site is located, prompting intial speculation that Pyongyang had conducted another nuclear weapons test, reports Efe news.

Each of the five tests carried out so far in Punggye-ri generated seismic activity, similar to that associated with earthquakes.

The tremor was initially believed to be caused by a nuclear test. However, the USGS soon dismissed that possibility, confirming that the tremor was recorded at a depth of 559.1 km.

There was no information from North Korea on the extent of damages or casualties caused by the quake.