Japan's chief government spokesperson said Japan would consider further unilateral sanctions against North Korea. He added, however, that the magnitude of the quake suggested it was not a test of a hydrogen bomb, as North Korea had claimed to have tested in January. "We can't deny the possibility that North Korea is miniaturizing a device to build a warhead," Inada said. Japan's Defense Minister Tomomi Inada told a press briefing that the country's test and advances in missile technology posed a grave threat to Japan. White House Press Secretary Josh Earnest said later that Obama promised "serious consequences" for provocative actions by North Korea, and reiterated the U.S.'s commitment to the security of its Asian allies. White House, said that the two leaders agreed to use every available means to pressure North Korea to abandon its nuclear program. The Blue House, South Korea's version of the U.S. president headed back to the United States from a regional summit in Laos. South Korean President Park Geun-hye, who described the North's actions as "maniacal recklessness," held an unscheduled phone call with Barack Obama to discuss the issue, as the U.S. Meanwhile, Jeffrey Lewis of the Middlebury Institute of International Studies told Reuters that the seismic activity detected in North Korea indicated a blast of 20 kilotonnes to 30 kilotonnes, which he said would make the test larger than the nuclear bomb the U.S dropped on Hiroshima in World War II and possibly even larger than the one dropped on Nagasaki soon after. The South Korean military said the magnitude 5.0 seismic wave would indicate a 10 kilotonne blast, which would be the isolated nation's largest ever, local news agency Yonhap reported. The agency said the "man-made" quake emitted energy double that emitted by the January nuclear test. The blast caused by the test was bigger than the one caused by North Korea's nuclear test in January, according to the South Korean meteorological agency. Prior to North Korea's confirmation of the test, both Japanese and South Korean authorities said that they believed the explosion, which caused an earthquake, was the result of fifth nuclear test by their neighbor.
The statement from the rogue nation came after multiple global agencies detected seismic activity in North Korea on Friday morning local time.
In a rambling statement, North Korea said the successful test was a demonstration of the country's preparation for retaliation against its enemies, chiefly "U.S.-led hostile forces who have gone desperate in their moves to find fault with the sovereign state's exercise of the right to self-defense while categorically denying the DPRK's strategic position as a full-fledge nuclear weapons state."