North Korea said it successfully tested a powerful nuclear bomb on Wednesday, drawing threats of further sanctions even though the United States and weapons experts voiced doubts the device was as advanced as the isolated nation claimed.
The underground explosion shook the earth so hard that it registered as a seismic event with U.S. earthquake monitors. It put pressure on China to rein in neighboring North Korea.
The U.N. Security Council said it would begin working immediately on significant new measures in response to North Korea, a threat diplomats said could mean an expansion of sanctions.
North Korea has been under Security Council sanctions since it first tested an atomic device in 2006. After a nuclear test in 2013, the Security Council took about three weeks to agree a resolution that tightened financial restrictions and cracked down on Pyongyang’s attempts to ship and receive banned cargo.
In the United States, Republican presidential candidates seized on the test to accuse President Barack Obama of running a “feckless” foreign policy that enabled North Korea to bolster its nuclear arms capabilities.
U.S. congressional sources said Republican leaders of the U.S. House of Representatives were considering a vote as soon as next week to broaden sanctions against North Korea by imposing stiffer punishments on foreign companies doing business with Pyongyang.
While North Korea has a long history of voicing bellicose rhetoric against the United States and its Asian allies without acting on it, the assertion by Pyongyang on Wednesday that it had tested a hydrogen device, much more powerful than an atomic bomb, came as a surprise.
North Korea also said it was capable of miniaturizing the H-bomb, in theory allowing it to be placed on a missile and potentially posing a new threat to the U.S. West Coast, South Korea and Japan.
The U.S. State Department confirmed North Korea had conducted a nuclear test but the Obama administration disputed the hydrogen bomb claim.
“The initial analysis is not consistent with the claim the regime has made of a successful hydrogen bomb test,” White House spokesman Josh Earnest told reporters. He said any nuclear test would be a “flagrant violation” of Security Council resolutions.
The explosion drew criticism, including from China and Russia. Beijing, the North’s main economic and diplomatic backer, said it will lodge a protest with Pyongyang.
Wednesday’s nuclear test took place two days ahead of what is believed to be North Korean leader Kim Jong Un’s birthday.
“Let the world look up to the strong, self-reliant nuclear-armed state,” Kim wrote in what North Korean state TV displayed as a handwritten note.
North Korea called the device the “H-bomb of justice.”
While the Kim government boasts of its military might to project strength globally, it also plays up the need to defend itself from external threats as a way to maintain control domestically.
It will likely take several days to determine more precisely what kind of nuclear device Pyongyang set off as a variety of sensors, including “sniffer planes,” collect evidence.