North Korea appears to be continuing its work to restore the Punggye-ri nuclear test site, which it ostensibly demolished in 2018 ahead of a historic summit with the United States, according to a North Korea information provider that cited satellite photos.

Commercial satellite imagery taken on April 26 of the site in Kilju, North Hamgyong Province, indicates ongoing work to restore access to the site's Tunnel No. 3 complex, with the construction of a new portal, or entrance, and support structures, read a note by 38 North.

"It is unclear if the portal has been completed yet, given the small amount of spoil that has been observed so far," it added. "The area outside the new portal has been leveled and stabilized. At the east end of the leveled area, the construction of a small support building has been completed."

In 2018, the North announced the complete closure of the Punggye-ri site, known to have four tunnels, with its demolition carried out in front of a small group of invited foreign journalists. Speculation has been widespread that the North may be preparing for its first nuclear test since September 2017. (Yonhap)