Sept. 23 (UPI) -- A 3.0 magnitude earthquake detected near North Korea's nuclear test site Saturday is presumed to have been a natural quake, South Korea's weather agency said.
The tremor occurred at 5:29 p.m., some 20 kilometers southeast of the country's Punggye-ri nuclear test in the northeastern province where the North conducted its sixth nuclear test on Sept. 3, according to the Korea Meteorological Administration.
"The quake has been analyzed to have occurred naturally," an agency official said. "A sound wave, which is usually generated in the event of an artificial earthquake, was not detected."
The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) said that it detected two seismic events in North Korea, but they were "unlikely (to have been) man-made."
But Japan's Kyodo News earlier reported that a 3.4 magnitude earthquake was detected at a depth of zero kilometers near the North's nuke test site, citing China's quake agency.
It said that it was thought to be an artificial quake caused by a "suspected explosion."
The quake occurred at a sensitive time when North Korea is likely to make further provocative acts after its leader pledged to retaliate against the United States.
North Korean leader Kim Jong-un has vowed to take the "highest-level" action in response to U.S. President Donald Trump's threat to "totally destroy" the North over its nuclear and missile programs.
North Korean Foreign Minister Ri Yong-ho said later in New York that Pyongyang may consider its most powerful test of a hydrogen bomb over the Pacific Ocean.
The North conducted its sixth and most powerful nuclear test in September. It claimed that it had detonated a hydrogen bomb for an intercontinental ballistic missile.
China announced Saturday that it will limit exports of petroleum products to North Korea starting in October to implement the latest U.N. sanctions over Pyongyang's sixth nuclear test.