Satellite photos show activity at Iran's Natanz nuclear facility

Iran has begun construction at its Natanz nuclear facility, satellite images show, and the UN’s nuclear agency has acknowledged that Tehran is building an underground advanced centrifuge assembly plant after its last one exploded in a reported sabotage attack last summer.

Since August, Iran has built a new or regraded road to the south of Natanz towards what analysts believe is a former firing range for security forces at the enrichment facility, images from the San Francisco-based Planet Labs show.

A satellite image on Monday shows what appears to be construction equipment. Analysts from the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies say they believe the site is undergoing excavation.

“That road also goes into the mountains, so it may be the fact that they’re digging some kind of structure that’s going to be out in front and that there’s going to be a tunnel in the mountains,” said Jeffrey Lewis, an expert at the institute who studies Iran’s nuclear programme. “Or maybe that they’re just going to bury it there.”

Iran’s mission to the United Nations did not immediately respond to a request for comment.

Ali Akbar Salehi, the head of the Atomic Energy Organization of Iran, told state television last month that the destroyed above-ground facility was being replaced with one “in the heart of the mountains around Natanz”.

Rafael Grossi, the director-general of the International Atomic Energy Agency, said his inspectors were aware of the construction work. He said Iran had previously informed IAEA inspectors, who continued to have access to Iran’s sites despite the collapse of the 2015 nuclear deal between Iran and world powers.

“It means that they have started, but it’s not completed. It’s a long process,” Grossi said.

Donald Trump’s campaign against Iran has led Tehran to abandon all limits on its atomic programme, and the heightened tensions between the US and Iran nearly ignited a war at the start of the year. Trump’s challenger in next month’s US election, Joe Biden, has expressed a willingness to return to the 2015 accord.