SEOUL, South Korea (AP) -- South Korea says it suspects a nuclear test caused an earthquake Tuesday in North Korea just north of a site where the country conducted two previous atomic tests. North Korea has yet to confirm whether the tremor resulted from a widely anticipated third nuclear test.
A U.N. nuclear test monitoring organization says it detected what it's calling an "unusual seismic event" in North Korea.
One South Korean earthquake specialist says "there is a high possibility that North Korea has conducted a nuclear test." He says a magnitude 3.9 earthquake and a magnitude 4.5 quake were detected in the North's 2006 and 2009 nuclear tests.
Earlier Tuesday, North Korea's powerful politburo vowed to continue firing "powerful long-range rockets," but a statement by state media made no mention of a nuclear test.
Last month, North Korea's National Defense Commission said the United States was its prime target for a nuclear test and long-range rocket launches.