VIENNA (AFP/Reuters) - The UN atomic watchdog on Tuesday said it had credible information Iran was working on developing nuclear weapons, its toughest-talking assessment yet which Tehran rejected as baseless. The information that Iran last month moved a large cylinder with LEU to the Fordow subterranean site was included in the UN bodys report pointing to military aspects of Tehrans nuclear programme. The International Atomic Energy Agency said it had serious concerns based on credible information indicating that the Islamic republic has carried out activities relevant to the development of a nuclear explosive device. The United States said the report showed that Iran had lied and said it would seek to ratchet up pressure and may seek new sanctions, but analysts said the report would not be enough to get China and Russia on board for such a move. Although some of the activities listed in 12 dense pages of intelligence have civilian as well as military applications, the keenly-awaited report said that others are specific to nuclear weapons. Irans envoy to the Vienna-based IAEA, Ali Asghar Soltanieh, told the Iranian news agency Fars that the report was a repetition of old claims which were proven baseless by Iran in a precise 117-page response. The envoy said his country will never compromise its legitimate rights in pursuing its atomic programme. As a responsible state, the Islamic republic of Iran will never compromise its legitimate rights and will continue to comply with its commitments under the nuclear Non-Proliferation Treaty, Soltanieh said, as cited by the official IRNA news agency. Iran will continue its peaceful nuclear activities. And, just as many other previous claims were proven baseless, this time also they will not bear any results, he said. Soltanieh stressed that Irans nuclear programme was entirely peaceful and that Iran would continue to cooperate with the International Atomic Energy Agency, the UNs nuclear watchdog. Using input from more than 10 foreign intelligence agencies plus its own information, the IAEA report listed in considerable detail Iranian work in 12 areas that practically covered every area needed for a weapon. The picture is pretty comprehensive when you want to develop a nuclear weapon. It has the core itself, it has a delivery system, it has the acquisition of the material, a senior official familiar with the IAEA probe said. These included computer modelling of a nuclear warhead; testing explosives in a large metal chamber at the sprawling Parchin military base near Tehran; and studying how to arm a Shahab 3 medium-range missile with an atomic warhead. If you put all of this information together it paints a picture that pretty clearly shows that they had nuclear weapons in mind, nonproliferation analyst Peter Crail from the Washington-based Arms Control Association told AFP. Iran is on very shaky ground trying to defend a lot of these activities. The IAEA, whose board could decide to report Tehran to the UN Security Council again next week, called on Iran to engage substantively with the agency without delay for the purpose of providing clarifications. US Senator John Kerry, head of the Senate Foreign Relations Committee, said the report made it clear that Iran has not been truthful and that the international community had to increase pressure on Tehran. But Iranian Foreign Minister Ali Akbar Salehi, speaking in Armenia before the report was released, said there was no serious proof that Iran is going to create a nuclear warhead. We have repeatedly stated that we are not going to create nuclear weapons, Salehi said. Our position has always been that we will never use our nuclear programme for purposes other than peaceful ones. President Mahmoud Ahmadinejad said his country does not need an atomic bomb and would instead act thoughtfully to confront US threats against it, according to state media. However he warned: If America wants to confront the Iranian nation, it will certainly regret the Iranian nations response. The hawkish foreign minister of Irans arch-foe Israel, Avigdor Lieberman, said before the release of the report that only crippling sanctions would be able to thwart Iran, the Maariv newspaper reported. The deputy chief of Irans armed forces, Brigadier General Masoud Jazayeri, warned Israel Wednesday it faced destruction if it attacked the Islamic republic. He stressed that the Israeli nuclear site of Dimona was the most accessible target, but also said our response would not be limited to the Middle East, according to an interview given to the Iranian Arabic-language channel Al-Alam. Russia meanwhile expressed anger over the publication of the report, saying it risked damaging the chance of a renewal of nuclear talks, saying it was gravely disappointed and bewildered. Earlier Russian President Dmitry Medvedev, speaking in Berlin, said that Israeli threats were extremely dangerous rhetoric that could result in a catastrophe for the Middle East. Germanys foreign ministry called for greater political and diplomatic pressure on Iran, while French Foreign Minister Alain Juppe said sanctions should be toughened but everything must be done to avoid a military conflict. In its previous report on Irans nuclear programme, in early September, the IAEA said Iran had installed one of two planned cascades, or interlinked networks of centrifuges. Such machines spin at supersonic speeds to increase the fissile isotope ratio. On October 17, the latest report said, Iran transferred ... one large cylinder containing LEU in the form of UF6 (uranium hexafluoride gas) and one small cylinder containing depleted uranium in the form of UF6. The uranium gas is fed into centrifuge machines to refine uranium for use either to fuel nuclear plants, Irans stated aim, or provide material for the core of a nuclear bomb, which the West fears is Irans ultimate goal. According to Iran, the LEU will be used for feeding and the DU will be used for line passivation, the IAEA report said, referring to technical preparations for starting enrichment. Iran only disclosed the existence of Fordow - tucked deep inside a mountain on a former military base - to the IAEA in September 2009 after learning that Western intelligence agencies had detected it. Tehran says it will use 20 per cent-enriched uranium to convert into fuel for a research reactor making isotopes to treat cancer patients, but Western officials say they doubt that the country has the technical capability to do that. Western experts say tightening sanctions, technical hurdles and possible cyber sabotage have slowed Irans atomic advances. But it is still amassing LEU; the IAEA report said it had produced a total of more than 4.9 tonnes since the work started in February 2007, some of which has been converted into 20 per cent material. This amount of low enriched uranium if further enriched to weapon grade is enough to make four nuclear weapons, said the Institute for Science and International Security, a Washington-based think tank.