Fears that three suspected nuclear sites are being shielded by the Iranian authorities were revealed by the UN’s atomic watchdog on Tuesday as it revealed Iran had nearly tripled its stockpile of enriched uranium. A report leaked from the inspectors said the build up had taken place in the space of three months and coincided with official refusal to provide clarification on three possible undeclared nuclear sites. The International Atomic Energy Agency issued a strong warning to member states in special report on Tehran’s nuclear programme that was released alongside the agency’s quarterly update. It is the first time the agency has issued an additional report since the 2015 agreement limiting Iran’s nuclear activity in exchange for sanctions relief was put in place. The IAEA found Iran now has five times the amount of enriched uranium than it is allowed under the terms of the 2015 deal. The secondary report revealed the agency had identified three possible undeclared locations where nuclear material may have been stored in secret, but had received no answers to its questions over the sites from Tehran. “The agency identified a number of questions related to possible undeclared nuclear material and nuclear-related activities at three locations in Iran that had not been declared by Iran,” the agency said. Iran, the agency said, had responded to its latest concerns in January saying it would “not recognise any allegation on past activities and does not consider itself obliged to respond to such allegations”. One of the sites, in the Turquzabad district of Tehran, was mentioned in the so-called “atomic archive” of information on Iran’s former nuclear weapons programme gathered by Israeli intelligence agents. Diplomats say the IAEA visited the site, gathering samples that showed traces of Uranium that Tehran has not yet fully explained. Israeli Prime Minister Benjamin Netanyahu, speaking at the United Nations General Assembly in 2018, said the site was "a secret atomic warehouse for storing massive amounts of equipment and material from Iran's secret nuclear weapons program". Iran has said the site is a carpet-cleaning facility. "The fact that we found traces (of uranium) is very important. That means there is the possibility of nuclear activities and material that are not under international supervision and about which we know not the origin or the intent,” the IAEA’s head Rafael Grossi said. “That worries me,” he added. The IAEA chief, in Paris for talks with French President Emmanuel Macron, said: "Iran must decide to cooperate in a clearer manner with the agency to give the necessary clarifications." The report revealed Iran had refused the watchdog access to two other possible undeclared nuclear sites it tried to visit in January. Iran denies ever having had a nuclear weapons programme and says it would never seek to obtain a nuclear weapon. It has, however, systematically breached the deal's restrictions on its atomic activities in response to Washington's withdrawal from the deal in May 2018 and its reimposition of sanctions that have choked off the Islamic republic's vital oil exports. The Trump administration says its "maximum pressure" campaign will force Iran to negotiate a more sweeping deal than the strictly nuclear agreement. Washington wants a broader deal, covering issues such as Iran's ballistic missile programme and its role in Middle Eastern conflicts like those in Syria and Yemen. It also wants to ban Iran from enriching uranium altogether. Tehran says it will not negotiate unless US sanctions are lifted.