A Voice of America journalist tweeted that US government sources believe North Korea had placed a nuclear device in a tunnel and it could be detonated as early as this weekend.
It comes after Washington-based 38 North, a website that monitors North Korea, said satellite images from Saturday showed vehicles and trailers at the Punggye-ri test site and signs that communications cables may have been laid to a test tunnel.
The think tank said water appears to be being pumped out and was draining downhill “presumably to keep the tunnel dry for monitoring or communications equipment.
Earlier foreign journalists visiting North Korea have been told to prepare for a “big and important event” tomorrow.
About 200 foreign journalists are in Pyongyang as the country marks the 105th birth anniversary of its founding president Kim Il Sung on April 15, North Korea’s biggest national day called “Day of the Sun”.
Officials gave no details as to the nature of the event or where it would take place, and similar announcements in the past have been linked to relatively low-key set pieces.
Tensions are running high, with a U.S. Navy strike group steaming toward the western Pacific in a show of force and North Korea warning of a nuclear attack on the United States at any sign of American aggression.
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