North Korea Claims to have Successfully Detonated a Hydrogen Bomb

North Korea announced on Wednesday that it has successfully conducted a hydrogen bomb test, which is the fourth unsanctioned test that the country has carried out so far.

The note, written in Korean and signed by the leader, Kim Jong Un, which could be seen on state television, read, "Make the world ... look up to our strong nuclear country and labor party by opening the year with exciting noise of the first hydrogen bomb!"

World leaders, who have condemned North Korea's actions, have already planned a meeting to discuss how they will be responding to the alleged test. The United Nations Security Council will be holding the emergency meeting in New York.

"Regardless of whether this is a hydrogen test or a normal, vanilla device, this is a very serious provocation," James Acton, co-director of the nuclear policy program at the Carnegie Endowment for International Peace, said reported by the Washington Post.

Experts on nuclear bombs and the military in South Korea have expressed their skepticism about North Korea's claim because of the size of the blast, which they say is more similar to an atomic bomb as opposed to a hydrogen one.

"Unless North Korea has help from outside experts, it is unlikely that it has really achieved a hydrogen/fusion bomb since its last nuclear test just short of three years ago," defense analyst at Rand Corp, Bruce Bennett, commented.

CNN cited the U.S. Geological Survey, which reported that a seismic event of 5.1 magnitude occurred around 10 a.m. (8:20 p.m. ET on Tuesday) east-southeast of Sungjibaegam.

South Korean President Park Geun-hye did put her military on high alert. She added that North Korea should pay a price for conducting the test.

"Now, the government should closely cooperate with the international community to make sure that North Korea pays the corresponding price for the nuclear test," Park said reported by Yonhap News Agency according to the Post.

Other nations have also released statements condemning North Korea.

The Japanese Prime Minister Shinzo Abe said in front of reporters in Tokyo, "This nuclear test by North Korea is a major threat to our country's security, and I absolutely cannot accept it . Also, it is clearly a violation of United Nations Security Council resolutions so . . . we will take strong measures, including steps within the U.N. Security Council."

The U.S. State Department spokesman John Kirby, said, "While we cannot confirm these claims at this time, we condemn any violation of U.N. Security Council resolutions and again call on North Korea to abide by its international obligations and commitments. We have consistently made clear that we will not accept it as a nuclear state. We will continue to protect and defend our allies in the region, including [South] Korea, and will respond appropriately to any and all North Korean provocations."

Countries, including Japan and the U.S., have sent planes to try and collect fallout from the bomb for tests.

In December, North Korea claimed to have a hydrogen bomb. That claim was also met with a lot of cynicism.