Israel’s prime minister has unveiled what he said was a previously undisclosed Iranian nuclear weapons site, further escalating a showdown between the two countries.

Benjamin Netanyahu’s announcement came as the UN nuclear watchdog held a meeting in Vienna, where he is hoping the agency will take tougher action against Tehran.

It also came in the final stages of Israeli national elections, drawing criticism from opponents that the sudden press conference was a campaign stunt.

Speaking to reporters, Mr Netanyahu said Israel discovered the facility, in the central Iranian town of Abadeh, using information gathered in a trove of documents Israeli agents stole from an Iranian warehouse and made public early last year.

“Iran conducted experiments to develop nuclear weapons,” Mr Netanyahu said.

He provided no details or evidence of what the experiments were, but he showed two satellite photos. The first, taken in June, showed the facility intact, and the second, taken in July, showed parts of the building had been destroyed, in what he said was an Iranian cover-up after Israel discovered the facility.

“This is what I have to say to the tyrants of Tehran,” he said. “Israel knows what you’re doing, Israel knows when you’re doing it, and Israel knows where you’re doing it.”

Israel considers Iran to be its greatest enemy, and Mr Netanyahu has been a leading opponent to the international nuclear deal with Tehran. He says Iran is trying to build a nuclear bomb, a charge it denies, and has accused the Iranians of violating provisions of the agreement.

Iranian foreign minister Mohammad Javad Zarif posted on Twitter a 2002 video of Mr Netanyahu speaking about what he saw as the “positive reverberations” that would come with the overthrow of the late Iraqi dictator Saddam Hussein.

“The possessor of REAL nukes cries wolf_on an ALLEGED “demolished” site in Iran,” Mr Zarif said, referring to Israel’s never-acknowledged nuclear weapons programme.

He did not address what the Iranian site was or why it appeared to have been demolished.

Abadeh is a small city famous for its carpets located 300 miles south east of the Iranian capital.

There has been a longtime airport project planned for the area that authorities broke ground on in 1995. At one point, officials suggested it could become an air defence base. However, there’s been no major development at the site.

Benjamin Netanyahu speaks during a press conference
Benjamin Netanyahu speaks during a press conference (Tsafrir Abayov/AP)

GPS co-ordinates offered by Mr Netanyahu did correspond to a set of buildings in the hills north of Abadeh, according to commercially available satellite images, but their purpose could not be immediately determined.

Last year, President Donald Trump withdrew the US from the nuclear agreement and reimposed sanctions on Iran. The deal has steadily unravelled since then, and caused tensions to heighten across the Persian Gulf and broader Middle East.

Those tensions have spilled over into fighting between Israel and Iran and its Shiite allies in Lebanon and Syria. Earlier on Monday, Israel said Iranian-backed Shiite militants in Syria failed in an attempt to fire rockets into Israel, while the Lebanese militant group Hezbollah said it shot down an Israeli drone in Lebanese airspace.

The International Atomic Energy Agency, the UN nuclear watchdog, has said for years that Iran halted organised efforts at exploring a possible nuclear weapons in 2003. US intelligence officials have made the same conclusion.

In Vienna, the IAEA confirmed on Monday that Iran is preparing to use more advanced centrifuges, another breach of limits set in the unravelling nuclear deal.

Iran had already announced the step, its latest violation of the 2015 agreement as it tries to pressure European signatories to find a way to maintain oil shipments and ease the toll of US sanctions on the Iranian economy.