VIENNA - A US security institute published new satellite imagery on Wednesday which it said appeared to show further activity to clean up an Iranian military site which the UN nuclear watchdog wants to inspect, including removing earth.
Parchin, which Iran says is a conventional military complex, is at the center of Western allegations that Iran has conducted experiments - possibly a decade ago - that could help develop atom bombs. Iran denies any such ambition.
The Institute for Science and International Security (ISIS) published the latest satellite picture a day after Iran and six world powers failed to make any progress on their decade-old nuclear dispute during two days of talks in Moscow.
Iran has so far refused to grant the International Atomic Energy Agency (IAEA) access to the Parchin facility as part of the UN agency's long-stalled investigation into suspected nuclear bomb research in the Islamic Republic.
Western diplomats say they believe Iran may be trying to clean the sprawling site of any incriminating evidence before possibly allowing IAEA inspectors to go there.
Iran has dismissed the allegations, but IAEA Director General Yukiya Amano earlier this month said satellite images indicated that buildings were being demolished and soil removed at Parchin, about 30 km (20 miles) southeast of Tehran.
"I think there is real concern for what the Iranians are doing at Parchin," one Western envoy said on Wednesday.
Iran dismisses allegations
ISIS last month published imagery which it said increased concerns that Iran was trying to "destroy evidence" of suspected past research relevant for developing a nuclear weapons capability, including the razing of two small buildings.
On Wednesday, the think-tank posted a picture from June 7 on its website which "shows what appears to be further sanitization activity" at the site in the Parchin complex where Iran is suspected to have conducted high explosive tests.
"The image shows heavy machinery tracks and earth displacement throughout the site," ISIS, which monitors Iran's nuclear program closely, said.
Debris from one of two razed buildings that were visible in a May 25 image "has now been consolidated into piles", it said.
"There is evidence of earth moving machinery and excavation activity near the second demolished building north of the building suspected to contain the high explosive testing chamber," ISIS added.
Iran has dismissed allegations aired about Parchin as "childish" and "ridiculous" and earlier this month accused the IAEA of behaving like a Western-manipulated spy agency.
An IAEA report last November said Iran had built a large containment vessel in 2000 at Parchin in which to conduct explosives tests that the UN agency said were "strong indicators of possible weapon development".
It said a building was constructed around a large cylindrical object, a vessel designed to contain the detonation of up to 70 kg of high explosives. Diplomatic sources say the suspected tests likely took place about a decade ago.
ISIS said: "If Iran has nothing to hide, its activities at this site add a further layer of suspicion and negatively impact efforts to build confidence in the peaceful nature of Iran's nuclear program."