VIENNA: Iran resumed uranium enrichment at its underground Fordow nuclear facility by injecting uranium gas into centrifuges, Iran's Tasnim news agency quoted the country's Atomic Energy Organisation (AEOI) as saying on Thursday.
"After all successful preparations ... injection of uranium gas to centrifuges started on Thursday at Fordow ... all the process has been supervised by the inspectors of (the) UN nuclear watchdog," Tasnim reported, quoting the AEOI's statement.
A 2015 nuclear deal between Iran and major powers bans Fordow from producing nuclear material. But, with feedstock gas entering its centrifuges, the facility - built inside a mountain - will move from the permitted status of research plant to being an active nuclear site. "The process will take a few hours to stabilize and by Saturday, when International Atomic Energy Agency inspectors will again visit the site, a uranium enrichment level of 4.5% will have been achieved," AEOI's spokesman Behrouz Kamalvandi told state TV. Ninety percent purity is required for bomb-grade fuel.
Iran has gradually scaled back its commitments to the deal, under which it curbed its nuclear programme in exchange for the removal of most international sanctions, after the United States reneged on the agreement last year.
Under the pact, Iran agreed to turn Fordow into a "nuclear, physics and technology centre" where 1,044 centrifuges are used for purposes other than enrichment, such as producing stable isotopes, which have a variety of civil uses.
"All the centrifuges installed in Fordow are IR1 types. Uranium gas (UF6) was injected to four chains of IR1 centrifuges (696 centrifuges)," Kamalvandi said.
"Two other remaining chains of IR1 centrifuges (348 centrifuges) will be used for producing and enriching stable isotopes in the facility."
US President Donald Trump exited the deal, saying it was flawed to Iran's advantage. Washington has since renewed and intensified sanctions on Iran, slashing the country's economically vital crude oil sales by more than 80 percent.
The measure will further complicate the chances of saving the accord, which European powers have called on Iran to respect.
Responding to Washington’s "maximum pressure" policy, Iran has bypassed the restrictions of the deal step-by-step - including by breaching both its cap on stockpiled enriched uranium and on the fissile level of enrichment.
Earlier, it emerged that Iran briefly held an inspector for the IAEA and seized her travel documents, diplomats familiar with the agency's work said on Wednesday, some describing it as harassment.
The incident appears to be the first of its kind since Tehran's landmark deal with major powers was struck in 2015.
The issue is due to be discussed at a meeting of the IAEA's 35-nation Board of Governors on Thursday convened at short notice to discuss "two safeguards matters" not specified in the agenda, which was circulated on Monday.
"The agency wants to show how seriously they are taking this. It is a potentially damaging precedent," one Western official said.
Three diplomats familiar with the agency's work said the female inspector had her travel documents taken, and two said she was briefly held while working in Iran.
One of the diplomats said the incident occurred at Iran's enrichment site at Natanz last week. Another one also said the incident took place at Natanz.
"There is a real concern that it will harm how (the IAEA) carry out their inspections in the future," a European diplomat said.
The nuclear deal, which the IAEA is policing, allows for 130-150 inspectors from the agency designated for Iran.
