The incident occurred at a warehouse under construction at the Natanz nuclear complex in central Iran on July 2, but caused no casualties or radioactive pollution, according to Iran's nuclear body.

"What is certain is that in our view, a drone, missile, bomb or rocket attack is not the case," ISNA news agency quoted Mojtaba Zolnour, head of parliament's national security and foreign affairs committee, as saying.

"There are traces of an explosion from elements on the inside (of the building) but since investigations are ongoing, I will not disclose the details," he added.

Iran's Supreme National Security Council announced on July 3 that the "cause of the accident" at Natanz had been "accurately determined" but declined to release details, citing security reasons.

State news agency IRNA at the time published an editorial warning Iran's arch-foes against hostile actions.

It said Israeli social media accounts had claimed the Jewish state was behind the incident, without identifying the accounts.

A spokesman for the Iranian Atomic Energy Organisation has acknowledged that the incident caused "significant financial damage" and that the building had been designed to produce "advanced centrifuges."

Tehran announced in May last year it would progressively suspend certain commitments under a 2015 landmark nuclear deal with major powers.

The United States unilaterally abandoned the accord in 2018.

Iran restarted enriching uranium at Natanz last September, despite having agreed under the accord to put such activities there on hold.

Tehran has always denied its nuclear programme has any military dimension.