Iran has called Israeli Prime Minister Benjamin Netanyahu “an infamous liar” over allegations he made about a secret Iranian nuclear weapons programme.
Mr Netanyahu’s revelations have split Western powers, days before the US is due to decide on whether to withdraw from the 2015 nuclear deal with Iran.
France said some of the information had been disclosed in 2002, and stressed the importance of continuing the deal.
The US, however, said it was proof it had not been built on good faith.
US President Donald Trump, who opposes the accord, has until 12 May to decide whether to abandon it or not.
Other signatories to the deal, including the UK and France, say Iran has been abiding by it and it should be kept.
What did Iran say?
Foreign Ministry spokesman Bahram Ghasemi said allegations by Mr Netanyahu that Tehran had lied about its nuclear ambitions were “worn-out, useless and shameful”.
Iran’s Foreign Minister Javad Zarif earlier said it was a move by Mr Netanyahu to influence Mr Trump’s decision on whether the US should stick with the nuclear deal.
He said the documents were a rehash of old allegations already dealt with by the International Atomic Energy Agency (IAEA), which has been tasked with investigating Iran’s nuclear past.
How has the IAEA reacted?
It failed to directly address Mr Netanyahu’s accusations but referred to an agency report from 2015 which had found some activities in 2003 “relevant to the development of a nuclear explosive device”.
But it also said the same report had “no credible indications of activities in Iran relevant to the development of a nuclear explosive device after 2009”.
What was in the documents?
Mr Netanyahu on Monday presented what he said was evidence of thousands of “secret nuclear files” that showed Iran had lied about its nuclear ambitions before the deal was signed in 2015.
He accused Iran of conducting a secret nuclear weapons programme, dubbed Project Amad, and said it had continued to pursue nuclear weapons knowledge after the project was shuttered in 2003.
That followed the revelation in 2002 by an exiled Iranian opposition group that Iran was constructing secret nuclear sites in breach of the nuclear Non-Proliferation Treaty, of which Iran was a signatory.
Tension between the long-standing enemies has grown steadily since Iran built up its military presence in Syria, which lies to the north-east of Israel.
Iran has always denied seeking nuclear weapons, and agreed three years ago to curb its nuclear energy programme in return for the lifting of sanctions.
The Israeli leader did not provide evidence that Iran had violated the accord since it went into effect in early 2016. But he insisted that Project Amad had continued at the Iranian Defence Ministry – citing the head of the programme as saying: “Special activities will be carried out under the title of scientific know-how developments.”
What does the US say?
The White House initially responded to Mr Netanyahu’s allegations by saying they were consistent with its understanding that Iran “has” a “robust, clandestine nuclear weapons” programme.
However, it later corrected the statement by changing the tense of the verb to “had”, blaming a “clerical error”.
“The information presented by Prime Minister Netanyahu adds new and compelling details about these efforts,” a US National Security Council spokesperson added.
New US Secretary of State Mike Pompeo said the documents were proof “beyond any doubt” that “the Iranian regime was not telling the truth” and had hidden a “vast atomic archive from the world and from the IAEA”.
Meanwhile, Rob Malley, who was on the Iran negotiating team under the Obama administration, played down Israel’s allegations, saying they were “nothing new”.
What about other key players?
France’s foreign ministry said the Israeli intelligence findings had only reinforced the importance of the deal and “could also confirm the need for longer-term assurances on the Iranian programme”.
Donald Trump has asked for permanent restrictions on Iran’s uranium enrichment.
The evidence appeared to confirm what European powers had known for more than a decade and a half, France added.
A spokesman for the UK government said it would continue to back the deal, adding: “We have never been naive about Iran and its nuclear intentions.”
EU Foreign Policy Chief Federica Mogherini said the documents had not put into question Iran’s compliance with the deal and said they should be analysed by the IAEA.
What is the 2015 deal?
The agreement signed between Iran, the US, China, Russia, Germany, France and Britain lifted crippling economic sanctions in return for curbs on Tehran’s nuclear programme.
Under the Joint Comprehensive Plan of Action (JCPOA), Iran is committed to slashing the number of its centrifuges, which are machines used to enrich uranium.
It is also meant to cut its stockpile of enriched uranium drastically and not enrich remaining uranium to the level needed to produce nuclear weapons.
Why is Trump so unhappy?
He has described the deal as the “worst ever” and has twice already refused to certify to Congress that Iran is complying with the agreement.
He has warned that the US would withdraw completely on 12 May – the next deadline for waiving sanctions – unless European signatories to the deal and Congress address his concerns.
The US leader is unhappy that it only limited Iran’s nuclear activities for a fixed period and had failed to stop the development of ballistic missiles.
He also said it had handed Iran a $ 100bn (£72bn) windfall that it used “as a slush fund for weapons, terror, and oppression” across the Middle East.