Iran announced Friday it was activating new advanced centrifuges – which enrich uranium for the country’s nuclear program – after the United Nations’ nuclear watchdog criticized the country for not cooperating with the agency.

The U.N. nuclear watchdog’s board has condemned Iran for failing to cooperate fully with the agency, the second time it has done so in just five months.

The International Atomic Energy Agency also called on Tehran to provide answers in a long-running investigation into uranium particles found at two locations that Tehran has failed to declare as nuclear sites.