"An accident occurred on Thursday morning and damaged a warehouse under construction in open space at the Natanz site" in central Iran, said Behrouz Kamalvandi, spokesman for the country's Atomic Energy Organisation.

Kamalvandi was further quoted as saying that the complex is currently inactive and there is no risk of radioactive pollution.

The accident did not result in casualties, he added, noting that the cause was under investigation.

He did not give any details on the nature of the reported accident.

Tehran announced in May last year that it was suspending certain commitments under a multilateral nuclear deal unilaterally abandoned by the United States in 2018.

The 2015 accord promised Iran sanctions relief in exchange for limiting its nuclear programme.

US President Donald Trump's withdrawal from the deal was followed by Washington reimposing biting unilateral sanctions.

The Natanz facility is one of Iran's main uranium enrichment plants.