North Korea's Nuclear Program in the Spotlight

While much of the world's attention has been on Iran lately, and rightfully so, the North Koreans continue with their own preparations. Japan reports that they're finding the North Koreans are busy at a suspected nuclear test site. The Japanese are boosting surveillance, but they don't know for sure what the North is up to.

The vehicles have been seen in recent days at what is thought to be a nuclear testing site in the northeast of North Korea, Kyodo News agency reported, citing an unnamed government official.

It was unclear whether any nuclear tests by the North were imminent, but Japan is closely monitoring the situation, the official was quoted as saying.

The Japanese Foreign Ministry said Tokyo had boosted surveillance of the area and would continue to closely analyze intelligence, but said the government would not discuss specifics because of the sensitivity of the matter.

Defense officials also refused to confirm the Kyodo report.

American media reported last week that U.S. officials were monitoring potentially suspicious activity at a suspected underground nuclear site.

The report sent diplomats in the region scrambling to avert a possible test and get the North to return to multinational talks on its nuclear ambitions, which have stalled since November.

South Korea on Wednesday warned North Korea not to conduct a nuclear weapons test, saying it would further isolate the communist regime, while countries launched new efforts to persuade the North to resume stalled disarmament talks.

South Korea's Foreign Minister Ban Ki-moon said a nuclear test by North Korea would be much more serious than its July missile tests and create a "threatening situation that will shake the foundation of the global nonproliferation system and will further isolate the North."