Israel’s retaliatory strike on Iran three weeks ago destroyed a secret nuclear weapons research facility, according to the US-based news site Axios, citing American and Israeli officials.

It had been thought that Iran’s nuclear sites had escaped attack following US diplomatic pressure on Israel to avoid the risk of triggering all-out war.

Axios quoted a US official saying, “They conducted scientific activity that could lay the ground for the production of a nuclear weapon. It was a top secret thing.”

Most of the Iran government was unaware of what was going on there, the official said.

Among the targets Israel struck in response to an Iranian missile barrage before Rosh Hashanah was the military complex at Parchin, southeast of Tehran.

The Taleghan 2 facility at Parchin had previously been used to test explosives to set off a nuclear device, according to the Institute for Science and International Security, before Iran halted its nuclear weapons programme in 2003.

Iran has denied interest in the production of nuclear weapons.

However, American and US intelligence were concerned to detect research activity at the location last year that could be used for nuclear weapons and the US privately warned Iran against continuing, Axios reported.

A US official told the website that last month’s strike against Taleghan 2 “was a not so subtle message that the Israelis have significant insight into the Iranian system even when it comes to things that were kept top secret and known to a very small group of people in the Iranian government”.