Iran informed the IAEA two weeks ago it would rapidly expand its enrichment capacity at Fordow by adding eight cascades, or clusters, of IR-6 centrifuges at Fordow within three to four weeks.
Within two days the IAEA had verified that two of the cascades had been installed. In a confidential report to member states on Friday seen by Reuters, the agency said that number had now doubled.
"The Agency has verified that Iran has installed four of the aforementioned eight IR-6 cascades in Unit 1 at FFEP (Fordow Fuel Enrichment Plant)," the report said, adding that the verification was carried out on Sunday.
"Iran has not specified to the Agency when it would start feeding any of the cascades in Unit 1 with UF6 or the planned enrichment level," it added, referring to uranium hexafluoride gas, the feedstock for centrifuges.
The IAEA has released several damning reports about Iran’s nuclear progress in recent weeks.
The IAEA's most recent report determined that Iran has started up new cascades of advanced centrifuges and plans to install others in the coming weeks after facing criticism over its nuclear program.
The UN agency released a report at the end of May which found that Iran has further increased its stockpile of uranium enriched to near weapons-grade levels.
On Thursday, the United States announced new sanctions targeting Iran's oil trade on Thursday, saying it was acting in response to "steps (by Iran) to further expand its nuclear program in ways that have no credible peaceful purpose".
In the wake of the recent IAEA reports, the Group of Seven (G7) warned Iran against advancing its nuclear enrichment program and said they would be ready to enforce new measures if Tehran were to transfer ballistic missiles to Russia.
In response, Iran called upon the G7 to distance itself from "destructive policies of the past". Israel National News - Arutz Sheva