The Atomic Energy Organization of Iran (AEOI) has started work on a fresh phase of scaling back commitments under the 2015 nuclear deal, which had seen Tehran's controversial nuclear program dramatically shrink.

AEOI spokesman Behrouz Kamalvandi said Iranian technicians are set to inject nuclear gas known as UF6 into centrifuges at the Fordow facility, a contentious site located south of the capital city of Tehran. "It is a great development because Fordow was not supposed to be reactivated," Kamalvandi declared.

Under the deal, activity at Fordow had been restricted to research and development with those 1,044 centrifuges spinning empty. The fuel injection — to be conducted before the eyes of the UN nuclear watchdog inspectors — is expected to effectively transform the center back into the active enrichment facility it once used to be. 

The new measures will also raise Iran's average daily production of uranium to 6 kilograms, close to the pre-deal capacity. Following the past three phases of commitment reduction, Iran says, its stockpile is now standing at 500 kilograms — well beyond the 300-kilogram cap agreed upon under the nuclear deal.