Iran appears to have built an extension to part of its Parchin military site since May, the UN nuclear watchdog said in a report obtained by the Reuters news agency on Thursday.
A resolution of the International Atomic Energy Agency's (IAEA) Parchin file, which includes a demand for fresh IAEA access to the site, is a symbolically important issue that could help make or break Tehran's July 14 nuclear deal with six world powers.
The confidential IAEA report obtained by the news agency says, "Since (our) previous report (in May), at a particular location at the Parchin site, the agency has continued to observe, through satellite imagery, the presence of vehicles, equipment, and probable construction materials. In addition, a small extension to an existing building" appeared to have been built.
The changes were first observed last month, a senior diplomat familiar with the Iran file said.
The IAEA says any activities Iran has undertaken at Parchin since UN inspectors last visited in 2005 could jeopardize its ability to verify Western intelligence suggesting Tehran carried out tests there relevant to nuclear bomb detonations more than a decade ago.
Iran has dismissed the intelligence as "fabricated".
Under a "road map" Iran reached with the IAEA parallel to its agreement with six global powers, it is required to give the Vienna-based watchdog enough information about its past nuclear activity to allow it to write a report on the long vexed issue by year-end.
American experts recently said that satellite images showed "renewed activity at a site" inside Parchin, which the West has suspected of being used for nuclear activities.
The experts said the images, taken after the nuclear deal was announced, raised "obvious concerns that Iran was conducting further sanitization efforts to defeat" verification by the IAEA.
Iran's UN mission called the reports "baseless", adding that construction work at the military complex, which also includes offices and residential buildings, is "quite normal".
Iranian Foreign Minister Mohammad Javad Zarif rejected the reports as well, saying they were “lies” spread by opponents of the nuclear deal with world powers and claiming the alleged “sanitization” at the site was simply “road construction”.
"Full and timely implementation of the relevant parts of the road-map is essential to clarify issues relating to this location at Parchin," the new IAEA report said, according to Reuters.
According to data given to the IAEA by some member states, Parchin might have housed hydrodynamic experiments to assess how specific materials react under high pressure, such as in a nuclear blast.
"We cannot know or speculate what's in the (extended) building … It's something we will technically clarify over the course of the year," the senior diplomat told Reuters. The report said the extended building was not the one that some countries suspect has housed the controversial experiments.
News of the alleged extension of Parchin comes as the IAEA has come under pressure for not publishing its "road map" agreement with Tehran, which Iran argues is “secret” and must not be divulged.
IAEA chief Yukiya Amano last week rejected as "a misrepresentation" suggestions from critics of the deal that the IAEA had quietly agreed to allow Iran to inspect sections of Parchin on the agency's behalf.