(CBS/AP) SEOUL, South Korea - South Korean intelligence officials say North Korea is digging a new underground tunnel in what appears to be preparation for a third nuclear test.
A report written by intelligence officials and shared Monday with The Associated Press says recent satellite photos show piles of dirt near the newly excavated tunnel's entrance.
The report says the excavation at the North's northeast Punggye-ri site is in its final stages. Experts say dirt is needed to fill up underground tunnels before a nuclear test.
The report's release comes as North Korea prepares to fire a long-range rocket April 12-16 that Washington and others say is a cover for testing missile technology that could be used to fire on the United States.
Ominously, both of North Korea's previous nuclear tests, in 2006 and 2009, have come on the heels of rocket launches which were condemned by the international community.
North Korean space officials have now moved all three stages of the rocket into position, and vowed Sunday to push ahead with their plan in defiance of the international warnings against violating a ban on missile activity.
The Associated Press was among foreign news agencies allowed a firsthand look at preparations under way at the coastal Sohae Satellite Station in northwestern North Korea.
North Korea announced plans last month to launch an observation satellite using a three-stage rocket during mid-April celebrations of the 100th anniversary of the birth of North Korean founder Kim Il Sung. The U.S., Japan, Britain and other nations have urged North Korea to cancel the launch, warning that firing the long-range rocket would violate U.N. resolutions and North Korea's promise to refrain from engaging in nuclear and missile activity.
North Korea has tested two atomic devices, but is not believed to have mastered the technology needed to mount a warhead on a long-range missile.