North Korea continues to develop its nuclear program by commissioning a light-water reactor and enriching nuclear fuel at an undeclared facility, according to the chief of International Atomic Energy Agency (IAEA), expressing deep regret over Pyongyang’s “clear violation” of U.N. Security Council resolutions.

Director General Rafael Mariano Grossi delivered his assessment in a statement to the IAEA’s Board of Governors on Wednesday. 

“The Agency has observed that the 5MW(e) reactor at Yongbyon was not operating between mid-August and mid-October. Our experts believe this would provide sufficient time to refuel the reactor and start its seventh operational cycle,” Grossi said, referring