A 3.4 magnitude earthquake has occurred in the northeastern part of North Korea, data published by the China Earthquake Networks Center (CENC) has said.

The CENC says the quake was likely caused by an artificial explosion, as it took place in the same location where North Korea’s sixth nuclear test occurred, Beijing’s Xinhua News Agency reported

Executive Secretary of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) Lassina Zerbo, however, said in a tweet that two events took place some 50 km from the site of previous nuclear tests, and that they were “unlikely Man-made”.

The first took place at 1208 North Korea time, and was, according to Zerbo, of a magnitude of 4.1.

The United States Geological Survey (USGS) earthquake monitoring service reported that an event took place at 1659 Pyongyang Time, was of a magnitude of 3.5, and took place at a depth of 5 km underground.

“This event occurred in the area of the previous North Korean Nuclear tests,” USGS said in a statement. “We cannot conclusively confirm at this time the nature (natural or human-made) of the event.”

“The waveforms for this event are different than previous events at the site. The depth is poorly constrained and has been held to be 5 km by the seismologist.”

South Korea’s weather agency has stated that it may have been a natural event, Seoul’s Yonhap News Agency has said.

“As a result of analysis on the earthquake waveform, it appears a natural earthquake,” multiple South Korean media reported, quoting an official at Korea Meteorological Administration (KMA).

“Sound waves were not detected at the observatory detecting soundwave in Yanggu and Cheorwon in Gangwon Province,” the statement continued.

“The place where the earthquake happened is 20 kilometers southeast from the site where the sixth nuclear test was conducted.“

South Korea’s Meteorological Administration (KMA) confirmed has, however, confirmed an event of 3.0 magnitude and said it occurred in the Kilju area of North Hamgyeong Province.

If it is a nuclear test, the low magnitude of the earthquake event suggests a much smaller yield compared to the September 3 hydrogen bomb test, which triggered a 6.3 magnitude seismic event.

A further possibility, in the event the tremor was not caused by a nuclear detonation, is that tunnel infrastructure at North Korea’s testing site collapsed to some extent.

The event follows a turbulent week between the U.S. and North Korea, with leaders Donald Trump and Kim Jong Un trading insults.

North Korea’s foreign minister Ri Yong Ho is set to address the United Nations General Assembly in New York this afternoon.

Main picture: Korea Meteorological Administration