The Punggye-ri test site in North Korea is seen in an image from Airbus Defense and Space and 38 North. Photograph: (Reuters)
Satellite images show boxes or material kept around the side of the main building and a truck or a group of vehicles parked on the site
North Korea may conduct another nuclear test as commercial satellite imagery shows the nuclear site to be bustling with activity in three of its tunnel complexes.
North Korea has already conducted two nuclear tests this year, in January and September, and five in total. The previous tests were held in 2006, 2009 and 2013.
Satellite images show boxes or material around the side of the main building and a truck or a group of vehicles parked on the site.
Continued activity around Punggye-ri Nuclear Test Site since October 1, coupled with a key political anniversary next week, has stoked concerns about there being another nuclear test shortly.
Pyongyang has a penchant for carrying out nuclear tests on major political dates. North Korea is set to celebrate its 71st anniversary of Workers' Party soon.
However, it remains unclear about the precise reason for the increased activity in the nuclear site.
38 North, a website that keeps a close eye on North Korea, said there might be other reasons for Punggye- ri Nuclear Test Site, located in northeast of the country, to be busy. "(Increased activity) may be for a number of purposes including collecting post-test data, sealing the portal or preparing for another test," the website said.
"There is also increased activity near one of the two entrances at the South Portal... although the portal is assumed to be capable of supporting a nuclear test once a decision is made to move forward," the post further said.
The South Portal may be fully capable of carrying out a nuclear test as excavation stopped in 2012, the website said.
South Korea has got nervous about the recent development, with an unnamed foreign ministry official telling AFP: "We believe that the North is ready to carry out a nuclear test."