SEOUL, Sept. 9 (Xinhua) -- South Korea's military believed that the Democratic People's Republic of Korea (DPRK) has conducted its "most powerful" nuclear test so far on Friday after the biggest-ever artificial earthquake was detected at a site where its fourth nuclear test was carried out earlier this year.
A South Korean Defense Ministry official told Xinhua that it was a fifth nuclear test according to a preliminary analysis, saying that artificial seismic waves of a 5.0-magnitude quake were detected at about 9:30 a.m. local time (0030 GMT) from the DPRK's main Punggye-ri nuclear test site.
The official said the 5.0 magnitude put its explosive yield at about 10 kilotons, which is the highest explosive yield yet of any DPRK atomic devices. The explosive yield of the previous nuclear test was estimated at 6 kilotons.
The most powerful test came just 8 months after Pyongyang detonated what it claimed was its first hydrogen bomb, the fourth of its nuclear device tests, on Jan. 6.
The official said that the Seoul military is analyzing details on what type of nuclear material was used and whether the test was successful.
The DPRK had previously tested atomic bombs every three years or so. Pyongyang carried out its first test in October 2006, followed by the second in May 2009 and the third in February 2013.
The size of artificial seismic activities from the DPRK's nuclear tests has gradually increased from 3.9 in the first test to 4.8 in the fourth. The explosive yield has risen from 0.4 kilotons to 6 kilotons in the same period.
Pyongyang has conducted a series of ballistic missile launches since top DPRK leader Kim Jong Un gave an order on March 15 to test a nuclear warhead and ballistic rockets capable of carrying the warhead "in a short time."
Earlier this week, the DPRK test-fired three Rodong ballistic missiles that traveled about 1,000 km and landed near Japan's territorial waters. On Aug. 24, a ballistic missile was launched from a DPRK submarine off its east coast, flying 500 km, the longest-ever distance by the DPRK.
Earlier, the European Mediterranean Seismological Centre revised the seismic tremor's magnitude from an initial 5.0 to 5.2. The U.S. Geological Survey saw the tremor as a 5.3-magnitude earthquake.
The U.S. monitoring agency said the magnitude was caused by an explosion, but it said it could not determine what type of explosion it may be.
China Earthquake Networks Center and South Korea's meteorological agency put the magnitude at 5.0. The Chinese seismological agency said it was a suspected explosion.
An unnamed government source was quoted as saying that the DPRK conducted another nuclear test to mark the country's National Day.
According to media reports, Pyongyang had been preparing for its fifth nuclear test ahead of the 68th anniversary of the founding of the state on Sept. 9.
Prime Minister Hwang Kyo-ahn convened an emergency meeting of the National Security Council (NSC) following the suspected test, the presidential office Cheong Wa Dae said. President Park Geun-hye is in her overseas trip to Laos.
