The White House on Monday condemned North Korea's nuclear test as a "provocative act" and called for immediate action by the UN Security Council.
The US Geological Survey said on Monday it had detected an earthquake of a magnitude of 4.2 degrees on the Richter scale in North Korea as the country announced its first nuclear test.
In a statement, the USGS said the quake was recorded at 7.05 am on Monday.
"It was a shallow event or very close to the surface," Rafael Abreau, a USGS geologist, said.
The USGS said the quake was located 385 kilometers northeast of the capital Pyongyang, 70 kilometers north of the North Korean town of Kimchaek and 90 kilometers southwest of the North Korean town of Chongjin.
North Korea's official Korean Central News Agency (KCNA) said Pyongyang had conducted its first ever nuclear test on Monday.