Seoul, Mar 7 (IANS): Rafael Grossi, director general of the International Atomic Energy Agency (IAEA), on Tuesday said that "deeply troubling" signs of activity are continuously being detected at North Korea's Punggye-ri nuclear testing site.

Grossi made the remarks amid speculation that the North appears to be preparing for what would be its first nuclear test since 2017, reports Yonhap News Agency.

"The Nuclear Test Site at Punggye-ri remains prepared to support a nuclear test, and we continue to see indications of activity near Adit 3 of the Test Site," he said in a statement to the board of governors.

"The reopening of the nuclear test site is deeply troubling."

He noted that the road to the former Adit 4 entrance has been rebuilt, though the agency has not observed any indications of excavation.

The secretive North also appears to be operating the 5-megawatt reactor and the reported centrifuge enrichment facility at the Yongbyon nuclear site, Grossi said.

"There were indications of possible tests of the light water reactor (LWR) cooling system in late September and early October, and changes to the LWR's cooling water outlet channel in October," he added.

North Korea voluntarily dismantled the Punggye-ri site in 2018 to show its willingness to denuclearise to the international community.

The country, however, is believed to have begun repairing the facility, the site of its all six nuclear tests so far.

Pyongyang conducted its sixth and last nuclear test in September 2017.