Updated 11:15 a.m. ET
North Korea confirmed it has conducted its fifth test of a nuclear weapon, the second this year. The test occurred Friday morning local time and triggered a magnitude 5.3 seismic event.
The North's state TV said the test "examined and confirmed" the design of a nuclear warhead intended for placement on a ballistic missile. It said there was no leakage of radioactivity. China's Ministry of Environmental Protection said radiation levels in its border region with North Korea were normal.
South Korea's Joint Chiefs of Staff estimates the yield was 10 kilotons, which is almost twice that of the January test and would be the country's largest blast yet. But analyses of yield in North Korea are notoriously difficult, given the country's mountainous terrain. South Korea says further analysis will continue.
This test follows the January detonation of a device the North claimed was a hydrogen bomb, which led to wide condemnation and tougher international sanctions. Pyongyang previously tested at Punggye-ri in 2006, 2009 and 2013.
North Korea is the only nation to conduct any nuclear tests in this century. Friday's test falls on a North Korean holiday: the 68th anniversary of North Korea's founding as a state.
The move comes against numerous calls from North Korea's allies and antagonists to refrain from more "provocative acts" following January's test and a February rocket launch.
In March, the United Nations Security Council passed Resolution 2270, which the U.S. calls the toughest package of sanctions on the North in two decades. China, a longtime ally of Pyongyang, signed on, signaling it too was weary of the North's threats to the security of the Northeast Asia region. Six months after those sanctions, North Korea is only increasing its missile launches and test frequency.
If the provocation-condemnation cycle seems like a Groundhog Day situation, it is. President Barack Obama acknowledged as much Thursday in a press conference before heading home from a trip to Laos, saying "when it comes to changing Pyongyang's behavior, it's tough."
"We will continue to put some of the toughest pressure North Korea has ever been under as a consequence of this behavior," Obama said. "Can I guarantee that it works? No. But it's the best option that we have available to us right now and we will continue to explore with all parties involved — including China — the means by which we can bring about a change in behavior."
Early Friday, a statement from White House Press Secretary Josh Earnest said the president had been briefed on the nuclear test, and that Obama "indicated he would continue to consult our allies and partners in the days ahead to ensure provocative actions from North Korea are met with serious consequences."
With the latest test, talk of heightening and expanding the current sanctions surely will begin. But numerous rounds of sanctions so far only have seemed to strengthen Kim Jong Un's resolve to show off his military might. Alongside the nuclear test, the North Korean military has sent a number of projectiles and missiles into the sea since March and kept up its anti-American and anti-South Korean rhetoric.
Some Korean observers say that because Kim Jong Un's regime seeks to derive its legitimacy by being a full-fledged nuclear state, no amount of financial squeeze will stop him.
"It's pretty incredible that we've come this far since the first nuclear crisis back in 1994," says Hahm Chaibong, head of the Asan Institute for Policy Studies, a Seoul-based independent think tank. "Things just got worse and much worse, and we don't seem to see a way to reverse that trend."
Beyond crippling North Korea financially, other options include diplomatic ostracism: Katharine Moon, Brookings Institution's SK-Korea Foundation Chair, has floated throwing North Korea out of the United Nations altogether, and written that nations with diplomatic ties with Pyongyang ought to pull their ambassadors. Asan Institute's Hahm says the "politically incorrect" option is all-out regime change, an option few are openly talking about just yet.
Haeryun Kang contributed to this story.
(SOUNDBITE OF ARCHIVED RECORDING)
UNIDENTIFIED SINGERS: (Singing in Korean).
RENEE MONTAGNE, HOST:
You're listening to North Korean state TV this morning celebrating that country's test of a nuclear weapon. North Korea confirmed what is its fifth test after neighboring countries detected a suspicious 5.3 magnitude earthquake in North Korea overnight.
This is the second North Korean nuclear test just this year alone. NPR's Elise Hu is in Seoul and joins us to talk more about this. Good morning.
ELISE HU, BYLINE: Good morning.
MONTAGNE: What more do we know about that test?
HU: Well, it happened on Founder's Day, marking the 68th anniversary of the founding of the current government. And this particular blast appears to be the most powerful one of the five that North Korea has conducted.
South Korea estimates the yield is at about 10 kilotons. This is an early estimate. That's about half the size of Hiroshima. But it would be North Korea's largest ever. And also, these tests are happening far more frequently. The last one, as you noted, was just nine months ago.
Previously, North Korea would wait two or three years between its nuclear tests. And, of course, we should note North Korea is the only country in the world that has conducted nuclear tests in the 21st century.
MONTAGNE: And this latest test, of course - immediately condemned throughout the world. And that includes North Korea's only real ally, China. So what is North Korea up to here?
HU: We can run down the responses real quick. South Korean President Park Geun-hye accused North Korean leader Kim Jong-un of, quote, "maniacal recklessness." China said it resolutely opposes the test and says it will lodge a diplomatic protest.
But Kim Jong-un really sees nuclear weapons as key to the legitimacy of the regime domestically. So he's not likely to change his policy. It's really baked in to North Korea's culture and system. In fact, the phrase, quote, "we are a full-fledged nuclear state" is even taught to elementary school students in North Korea as one of the key English phrases to know.
So the nuclear program, really, is playing to a domestic political audience, keeping the regime legitimate and playing up this idea to North Korean citizens that the North is constantly under threat by outside forces like South Korea and the United States.
MONTAGNE: And, of course, though the North is in violation of U.N. Security Council resolutions, there are already pretty harsh economic sanctions. So what to do?
HU: Right. These sanctions so far haven't been successful in preventing the test. The North still has the resources to pursue nuclear weapons development. One ongoing hole in the sanctions regime is that they're not fully enforced by China.
And because China is reluctant to cripple North Korea - because frankly, the status quo, you could argue, is more desirable to China than a unified Korea under the leadership of Seoul, which is friendly to the United States.
MONTAGNE: One of the things that's said about North Korea is that the regime is belligerent. Yes, but maybe even a little crazy - that it's, of course, an isolated power. But that regime is still around three generations later. And the North has been improving its nuclear capabilities. In fact, one might argue that North Korea sort of knows what it's doing playing a long game.
HU: That's a really good point, Renee. The view in Asia, of course, is that they're not crazy at all but quite strategically successful. North Korea is really effective in operating in this space where there's distrust between the United States and China - sort of playing the U.S. and China against one another.
So China seems to have implicitly accepted that North Korea has become a nuclear power. The U.S. and South Korea - every time they try to put up defenses, it angers China. So instead of getting China on the side of the United States, China actually ends up siding with North Korea. So North Korea has been very effective with that sort of diplomatic game.
So from Pyongyang's perspective, they're quite successful - no reason to change that strategy. And we should note this is a real thorny question. It's going to be one of the biggest foreign policy challenges for the next administration.
MONTAGNE: As President Obama himself said.
HU: That's right.
MONTAGNE: NPR's Elise Hu has been in Laos with the president and is now back at her home base in Seoul, South Korea. Thanks very much.
HU: You bet. Transcript provided by NPR, Copyright NPR.