North Korea's H-bomb test: What we know now

North Korea has been under U.N. sanctions since 2006, when it first purported to have tested a nuclear weapon. Wednesday's incident marked the fourth alleged test since then.

Here's what we know about the developing situation:

>> North Korea says test a reaction to the United States' nuclear arsenal

An anchor for state-run Korean Central Television announced news of the alleged bomb test midday local time Wednesday, according to NK News. The anchor said the move was necessary to stay safe against the U.S., which has a number of nuclear weapons.

"The U.S. has gathered forces hostile to (the) DPRK and raised a slanderous human rights issue to hinder (the) DPRK's improvement," the anchor said, according to NK News. "It is (therefore) just to have (an) H-bomb as self-defense against the U.S. having numerous and humongous nuclear weapons. The DPRK's fate must not be protected by any forces but DPRK itself."

>>It's not entirely clear whether the bomb tested was a hydrogen bomb

A South Korean spy agency cast doubt over whether the North's bomb was indeed a powerful hydrogen bomb, the South's Yonhap News Agency reported. Instead, intelligence said it may have been an atomic bomb.

The difference would lie in the chemical reaction used to create the bomb's blast. Hydrogen or thermonuclear bombs can be thousands of times more powerful than atomic bombs.

>> U.N. Security Council calls emergency meeting

The United Nations Security Council planned to gather for an emergency meeting at 11 a.m. ET Wednesday, according to a report from Reuters. Citing unnamed diplomats, the wire service noted the meeting would likely take place "behind closed doors."

"The United States and Japan have requested emergency Security Council consultations for tomorrow morning regarding North Korea's alleged nuclear test," Hagar Chemali, spokeswoman for the U.S. mission to the United Nations, said in a statement released to Reuters.

It was not immediately clear whether the U.N. would take action against North Korea.

>> White House hasn't confirmed earthquake happened because of a nuclear test

In a statement, White House officials said they continued to monitor the situation in North Korea but could not confirm a nuclear test had taken place.

National Security Council spokesman Ned Price said the U.S. was working “in close coordination with our regional partners.

“While we cannot confirm these claims at this time, we condemn any violation of UN 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 (North Korea) as a nuclear state.”

>> Leaders worldwide condemn the test

At an emergency National Security Council meeting in Seoul, South Korean President Park Geun-hye vowed to respond with might to the North's test.

“It's not only grave provocation of our national security, but also an act that threatens our lives and future,” she said, according to The Associated Press. “It's also a direct challenge to world peace and stability.”

Japanese Prime Minister Sinzo Abe said his country will take "strong action," against North Korea and called the latest test a threat to his nation's safety, The Associated Press reported.

"France condemns this unacceptable violation of Security Council resolutions and calls for a strong reaction from the international community," French President Francois Hollande said in a statement.

Even China, one of North Korea's last major allies, said it “firmly opposes” the nuclear test.