US think tank: New activity at N.Korea's nuclear test site

A group of researchers at a US think tank says North Korea appears ready for its seventh nuclear test, and new construction activity is being observed elsewhere at the same site.

The group at the Center for Strategic and International Studies, or CSIS, on Wednesday released its analysis based on satellite photos of the Punggye-ri test facility in the country's northeast.

The researchers say the images taken on Tuesday show that the refurbishment and construction work at Tunnel No.3, known as the South Portal, is "essentially complete."

They cite the view of South Korean officials that Pyongyang is currently prepared to conduct a nuclear test at any time.

The researchers also say a new wall under construction and construction materials are observed near the entrance of Tunnel No.4, or the West Portal. The tunnel was closed four years ago.

They say the new activity strongly suggests "an effort to reenable it for potential future testing."