North Korea detonated an underground nuclear explosion in the northeast of the country - its second nuclear test since 2006.
David Albright, President of the Institute for Science and International Security, has been following North Korea's nuclear program for many years.
"In 2006, it [North Korea] was trying to achieve an explosion of four kilotons and it only got about half a kiloton - so it was generally viewed as not very successful. This time, it looks to be anywhere from one to five kilotons and if North Korea was trying to get four kilotons, then you'd have to judge the test a success," he said.
Albright says as a comparison, the bomb the United States detonated over Nagasaki at the end of World War II had a yield of 20 kilotons.
In addition to the nuclear explosion, Pyongyang has over the past few days also tested several short range surface-to-air and surface-to-ship missiles.
Jim Walsh is a nuclear and North Korea analyst with the Massachusetts Institute of Technology [MIT, in Cambridge Mass.]. He questions the value of those tests.
"Back in the summer of 2006 around July 4, when the North Koreans had broken the moratorium on long-range missile tests and had their first long-range missile test in 10 years or so, they also fired off a bunch of short-range missiles. There really is no reason why you'd want to do these things together from a scientific or engineering point of view," he said.
For his part, Albright says the short-range missile tests were simply part of North Korea's military research and development program. However he says the missiles - which are not equipped to carry nuclear warheads - were fired to deliberately coincide with the underground nuclear test.
Experts are asking why would the North Koreans detonate a nuclear device at this time?
Jim Walsh says there are two theories.
"One says they are doing this for bargaining - that by creating a crisis, it improves their position when they enter negotiations," he explained. "And then a second thread of thought suggests that it's not for bargaining; it has nothing to do with external foreign policy or external affairs - but rather it is driven by internal political dynamics; that because there is some sort of political transition, a leadership transition going on with Kim Jong-il's health problems, that North Korea, like many countries in that situation, takes dramatic action to sort of reassert themselves and to give it an expression of strength at a time of uncertainty," he said.
The international community has strongly condemned Pyongyang's detonation of a nuclear device. But analysts say there is little it can do to pressure North Korea to end its nuclear weapons program.
Analysts also question the future of the six-party talks - a negotiating process that began in August 2003 bringing together representatives from the United States, Russia, China, Japan, South Korea and North Korea.
Pyongyang withdrew from the talks following international condemnation of its April 5 test launch of a long-range ballistic missile.
David Kay, former chief nuclear weapons inspector with the (Vienna-based) International Atomic Energy Agency, believes the talks - as he put it - are dead.
"Not only are they dead because the North Koreans have expressed no interest in returning to them - I think it is recognized in Washington at least and I think around the world that it would be foolish to reward the North Koreans' sending off a nuclear device by rushing back to talks," Kay said.
However David Albright says placing more sanctions on Pyongyang and, as he put it, continuing to demonize North Korea is not the way forward. He says the new U.S. administration must send a high-level mission to that country.
"Not to offer incentives. Not to offer threats either. But to go there and try to have a meeting with Kim Jong-il and say look, what's going on? Do you want this confrontation to escalate?" He asked. "And in a sense hold out an open hand: nothing in it, not gifts, not threats. But find out what's going on. Because history tells us that North Korea is happy to escalate in these kinds of conflicts and so who knows how that is going to end," he noted.
Albright says threatening North Korea with sanctions and isolation is guaranteed to create escalation and not capitulation.