North Korea announced on Jan. 6 that it successfully tested a hydrogen bomb underground, which would be a first for the nation (video below).
"If there's no invasion on our sovereignty we will not use nuclear weapon," the North Korean state news agency stated, according to CNN. "This H-bomb test brings us to a higher level of nuclear power."
North Korea has done three underground plutonium bomb tests in the past, but a hydrogen bomb is more powerful.
An unidentified Obama administration official told CNN that it may take days before the U.S. will be able to determine if this was truly a successful test of a hydrogen bomb.
The United States Geological Survey did measure a seismic event that had a magnitude of 5.1 happening east-northeast of Sungjibaegam, North Korea.
The China Earthquake Network Center described the seismic event as a "suspected explosion," notes AFP.
"Further analysis is necessary to determine whether it is an artificial or a natural quake," a spokesman for the Korea Meteorological Administration told the news wire.
Researchers at the US-Korea Institute at Johns Hopkins University in Baltimore said in December 2015 that North Korea appeared to be digging a new tunnel at Punggye-ri, a nuclear test site.