North Korea analysis website Beyond Parallel says that recent satellite imagery of the Punggye-ri nuclear test facility in the North shows new activity in the area.

In a report released Thursday, the website run by the Washington-based Center for Strategic and International Studies (CSIS) said the road leading to the collapsed access for Tunnel No. 4 has been completed while two new small buildings have recently been constructed in front of the collapsed entryway.

Citing imagery taken on April 21, the report said that although the recently observed activity is not a strong indication, the long-anticipated seventh nulcear test will most likely take place at the Punggye-ri nuclear test facility.

North Korea blew up tunnels No. Two to Four at the Punggye-ri site ahead of its summit with the U.S. in 2018.

However as denuclearization talks with Washington broke down, signs of restoration activities at the site were detected from early last year and by August, Tunnel No. 3 appears to have been restored.

South Korea's defense ministry told lawmakers last month that Pyongyang may conduct its seventh nuclear test to technically verify its mass production and deployment of nuclear warheads, and the test may happen at any time upon the leadership's decision.