U.N. poised to act against North Korea after latest nuclear test

Meanwhile, U.S. President Barack Obama spoke to the leaders of South Korea and Japan, who both joined the President in condemning the act. Obama reaffirmed the United States' defense commitments to both of its regional allies.

South Korean President Park Geun-hye's office added that the two leaders agreed "there should be a corresponding price for this nuclear test."

North Korea bragged Wednesday about the "spectacular success" of its first hydrogen bomb test, a defiant act that leader Kim Jong Un, in a statement read on state television, said would "make the world ... look up to our strong nuclear country."

But did it really happen?

The United States doesn't think so, with White House spokesman Josh Earnest saying, "The initial analysis is not consistent with the North Korean claims."

That analysis isn't definitive, though, with some experts saying it's possible Pyongyang detonated a different type of hydrogen bomb.

Norsar, a Norway-based group that monitors nuclear tests, noted this fact and estimated, based on the seismic readings, a blast equivalent to less than 10,000 tons of TNT, smaller than those of the atomic bombs used on Hiroshima and Nagasaki, and far less than thermonuclear weapons that typically are as potent as millions of tons of TNT.

The group later added that as this test took place deeper underground, it would be harder to monitor radiation and thus determine the type of weapon tested. The U.S., South Korea Japan and China are all testing for airborne or ground radiation in the region. So far, the South Korean and Japanese attempts have not found any evidence of radiation.

It's possible North Korea has a "boosted" weapon, one that uses a small amount of fusion to boost the fission process, but is not a hydrogen bomb, but whether there was a hydrogen element isn't known.

Indeed, given the secrecy surrounding North Korea, it may be difficult to ever know; the last test, in 2013, has experts split over whether the device detonated then was plutonium or uranium.

Even if it wasn't an H-bomb, there's little doubt that North Korea did conduct a new significant nuclear test despite persistent calls not to do so.

If it was, it would be a game changer, said Mike Chinoy, a fellow at the University of Southern California's U.S.-China Institute.

"But evidence seems to suggest it wasn't a full hydrogen bomb."

However, he said that with each test North Korean nuclear scientists get more data and as a result closer to being able to miniaturize nuclear weapons, a development that would allow the country to deploy nuclear weapons on long-range missiles.

"Whether it was a full H-bomb or not it is still a worrying development," he said.

The underground test, which happened at 10 a.m. (8:30 p.m. ET Tuesday), corresponded with a magnitude-5.1 seismic event centered 12 miles (19 kilometers) east-southeast of Sungjibaegam, according to the U.S. Geological Survey. That's comparable to readings from North Korea's most recent plutonium test in 2013.

"We won't know for another few days or weeks whether this was (a hydrogen bomb)," said Martin Navias, a military expert at King's College London. "It doesn't look like one; ... one would have expected it to be greater if it was an H-bomb."

After being briefed by his nation's military, South Korean lawmaker Shin Kyung-min questioned the credibility of the hydrogen bomb claim. Joo Ho-young, who heard from the nation's intelligence service, told reporters, "It could be different from a usual hydrogen bomb."

Count Bruce Bennett, a senior defense analyst at the nonpartisan Rand research group, among the skeptics. He said North Korea has had trouble "mastering even the basics of a fission weapon," so it's a big leap to think it could create an even more complicated hydrogen bomb.

Whether or not it's a hydrogen bomb, the test did get the world's attention.

"Any kind of nuclear test, like the one that North Korea conducted ... is provocative and a flagrant violation of United Nations Security Council resolutions," said Earnest.

And that -- sticking it to world and regional powers -- may be Pyongyang's aim.

"The present-day grim reality clearly proves once again the immutable truth that one's destiny should be defended by one's own efforts," North Korea's official KCNA news agency reported. "... The army and people of the DPRK will steadily escalate its nuclear deterrence of justice both in quality and quantity to reliably guarantee the future of the revolutionary cause."

China spoke out strongly against the latest test, saying it had no notice. Beijing had company, as leaders from around the world, including Russia and NATO, condemned the test, rare unanimity at a time of pervasive discord on issues like Syria's civil war, the Shiite-Sunni Muslim divide, Ukraine and migration.

The anger and danger were felt most in South Korea, which was split from the North seven decades ago.

"This is clearly a provocation and threatening the lives of people and safety," South Korean President Park said. "We have been continuously warning that (North Korea) will pay a price for conducting a nuclear test."

In its official statements, Pyongyang singled out the United States -- or, as it called it, "a gang of cruel robbers" and a "hideous nuclear criminal that has constantly posed nuclear blackmail for more than 70 years, seriously endangering mankind."

This latest nuclear test, following detonations in 2006, 2009 and most recently 2013, "puts the U.S. on the spot," according to Chinoy.

"Will any of their steps do anything to restrain North Korea?" he mused. "My guess is probably not."

Combined with its secrecy and seclusion, North Korea's us-against-the-world perspective and the fact it doesn't play by traditional rules make it unpredictable at best and dangerous at worst. Add nuclear weapons to the mix -- even if they aren't thermonuclear -- and Pyongyang could unleash devastation of a sort not seen in over 70 years.

That's when U.S. forces used atomic bombs on the Japanese cities of Hiroshima and Nagasaki, ending World War II. Minuscule in power compared with H-bombs, the two blasts nonetheless killed about 200,000 people.

While it has done little outwardly to develop its economy, North Korea has put a lot of focus on its military, carrying a huge standing army of 1.2 million active soldiers plus 7.7 million reservists in a country of 25 million people.

North Korea's conventional weaponry is dated, with limited effectiveness. That's one reason, experts speculate, Pyongyang has sought nuclear weapons: to project power internationally.

The possibility of Pyongyang being able to strike the U.S. mainland, even now, can't be ruled out. And there's no doubt that South Korea and Japan, two countries that Washington has long vowed to defend, are within reach.

David Albright, a former U.N. weapons inspector, called the latest nuclear test "largely a mystery" and surmised that North Korea didn't test a standard two-stage hydrogen bomb, in which an atomic blast sets off a thermonuclear explosion.

"North Korea can bluff," said Albright, the founder of the Institute for Science and International Security. "It can claim that it now knows how to achieve high yields with thermonuclear concepts. It is difficult to prove it does not."