A US think tank says recent satellite imagery shows new activity at North Korea's Punggye-ri nuclear test site.
The Center for Strategic and International Studies on Thursday released its analysis of the images taken on April 21.
The analysts say there has been activity around a tunnel whose entrance collapsed in 2018. They say construction of a road leading to the entrance has been completed and two new buildings have appeared in front of that entrance.
But they say there are no signs of activity around another tunnel where they believe preparations for a nuclear test were completed almost a year ago.