The new workshop replaces a nuclear facility in Karaj, near Tehran, after an attack there last year, which Iran said was an act of sabotage.

On Tuesday, the International Atomic Energy Agency (IAEA) completed installing surveillance cameras at the new site and removed the seals from the machines to produce components of centrifuges, equipment used to enrich uranium.

"On April 13, Iran informed the agency that the machines would start operating at the new workshop the same day," Director General Rafael Grossi said in his latest report on the Islamic republic's nuclear programme seen by AFP.

World powers are negotiating to revive a 2015 landmark agreement to rein in Iran's nuclear activities in exchange for sanctions relief.

The accord started to unravel in 2018 when then US president Donald Trump left the deal and re-instated sanctions, leading Iran to in turn step up its nuclear programme again.

Negotiations to return to the 2015 agreement started early last year. Negotiators say they are close to a conclusion, but have not manage to finalise all points yet.

Since last year, Iran has not allowed the IAEA to actively use its surveillance cameras. Instead, Tehran is storing the recordings while negotiations are ongoing.