Following North Korea’s Wednesday announcement that has “perfectly succeeded” in testing a hydrogen bomb, the US released a statement making clear that it will not accept North Korea as a nuclear state and, if necessary, will “respond appropriately to any and all North Korean provocations.”

North Korea said on Wednesday morning that it had “scientifically test-proved a miniaturized hydrogen bomb.” The announcement, made on North Korean state TV, came about an hour after a 5.1 magnitude earthquake was recorded close to North Korea’s nuclear test site, raising suspicions that the country was testing nuclear weapons.

While the quake was later confirmed to be the artificial result of a nuclear explosion, officials have not yet determined if the weapon tested was indeed a hydrogen bomb or a less-powerful atom bomb.

National Security Council spokesman Ned Price said that the US was aware of the seismic activity “in the vicinity of a known North Korean nuclear test site”, and that it had seen the claims of a nuclear test, but could not confirm them.

Several US officials expressed skepticism at the claim, saying that North Korea does not have the capability to produce a hydrogen bomb. The US plans to send specially equipped “sniffer” planes to the region to determine what kind of test was done, as well as monitor the ongoing situation.

“We are monitoring and continuing to assess the situation in close coordination with our regional partners,” Price said in his statement, adding, “We condemn any violation of UNSC [United Nations Security Council] Resolutions and again call on North Korea to abide by its international obligations and commitments.”

North Korea is known to have performed three previous nuclear tests, all of which were condemned by the international community and which led to tightening of restrictions and sanctions against the country.

However, North Korea remains defiant, calling its nuclear test a “measure for self-defense” to “protect the sovereignty of the country…from the ever-growing nuclear threat and blackmail by the US-led hostile forces”.

Price warned that there would be repercussions to the test. “We have consistently made clear that we will not accept [North Korea] as a nuclear state,” he stated.

“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.”