North Korean state television announced Wednesday the country "successfully" conducted it's first hydrogen bomb test. "The republic's first hydrogen bomb test has been successfully performed at 10 a.m. on Jan. 6, 2016, based on the strategic determination of the Workers' Party," the broadcaster said in a surprise announcement, according to DW.

The United States Geological Survey (USGS) said a 5.1 magnitute earthquake was detected close to the nuclear test site, according to CNN. The epicenter was located some 30 miles from Kilju city, close to the notorious Punggye-ri nuclear site.  .

The alleged thermonuclear bomb test was North Korea's fourth nuclear test. The secretive communist state conducted three previous nuclear tests in 2006, 2009 and 2013.

South Korean President Park Geun-hye, who called an emergency meeting of the National Security Council, termed North's alleged thermonuclear device test a "grave provocation" against national security. "South Korea in cooperation with the international community must make North Korea pay a price that corresponds to it carrying out its nuclear test," she said in the meeting, according to Korea Times. 

"This nuclear test is Pyongyang's fourth, and considering the state is claiming it is its first hydrogen bomb test, it may shake Northeast Asia's security landscape and fundamentally change the nature of North Korea's nuclear issue," the president said.

The United States also condemned the test saying that it will not accept any violation of United Nations Security Council (UNSC) resolutions. "We will continue to protect and defend our allies in the region, including the Republic of Korea, and will respond appropriately to any and all North Korean provocations," National Security Council spokesman Ned Price said, according to VOA News.