A seismic event detected in North Korea at around 9 a.m. local time on Friday (8:30 p.m. Thursday night Eastern) has been confirmed to be from a nuclear test by the Communist country. The test was North Korea's fifth, and its largest to date.

The event, which measured 5.3, was called a "possible explosion" by the USGS. It took place just ENE of Sungjibaegam, in the region of a known nuclear test site. 

Within several hours of the explosion, the Japanese government confirmed that the event was, as many had suspected, a nuclear test. They did not say how they had figured that out, however.

South Korea said the same thing, announcing that the test was twice as big as North Korea's previous one in January, and "slightly less than the Hiroshima bombing." South Korean president Park Geun-hye said that her northern neighbor was guilty of "maniacal recklessness." Asian stock markets fell in response to the news.

The United States was taking a more cautious approach. Ned Price, the United States National Security Council spokesperson, said, "We are aware of seismic activity on the Korean Peninsula in the vicinity of a known North Korean nuclear test site. We are monitoring and continuing to assess the situation in close coordination with our regional partners." As of this writing, President Obama was reportedly being kept advised of the situation.

The events came on the 68th anniversary of the founding of the North Korean government. As of yet, North Korea has not issued any statement about the explosion, either to confirm or deny that it was a nuclear test.