DigitalGlobe - ISIS

This satellite image from Friday shows earth displacement activity at the suspected high explosive testing site in Parchin, Iran. The U.N.'s nuclear watchdog has repeatedly asked Iran for access to the site as part of a long-stalled probe into suspicions that Tehran may be seeking the ability to assemble nuclear bombs.

VIENNA -- U.N. nuclear inspectors displayed new satellite imagery on Wednesday indicating that some small buildings had been dismantled and other possible clean-up work undertaken at an Iranian military site they want to visit.

One image from May 25 showed signs that "ground-scraping activities" had taken place at the Parchin facility, as well as the presence of a bulldozer, according to diplomats who attended a closed-door briefing by U.N. nuclear agency officials.

This will likely further strengthen Western suspicions that Iran is "sanitizing" the site of any incriminating evidence before allowing the International Atomic Energy Agency (IAEA) into the complex. "It is very clear," one Western envoy said.

Iran's IAEA envoy, Ali Asghar Soltanieh, dismissed such accusations by Western officials, telling reporters after the briefing that "this kind of noise and allegations are baseless".

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The images released by the Institute for Science and International Security's (ISIS) could hurt a tentative deal between the U.N.'s atomic watchdog aimed at giving inspectors wide access to scientists, documents and facilities allegedly related to nuclear-weapons work, The Wall Street Journal reported. 

Wednesday's disclosure followed inconclusive talks between Iran and six world powers in Baghdad last week to address concerns about the nature of its nuclear activities, which Iran says are aimed at generating electricity.

The images were posted on ISIS's website hours after diplomats said the International Atomic Energy Agency showed what appeared to be similar imagery at a closed-door briefing in Vienna. 

The agency has been pressing Iran to allow inspectors to visit the Parchin military facility, which the IAEA thinks could have been involved in testing of high explosives, the Wall Street Journal reported.

Western envoys who attended Wednesday's briefing earlier told Reuters that two small side buildings at Parchin had been removed, and ISIS said its pictures from May 25 showed that they "have been completely razed."  

ISIS, which tracks Iran's nuclear program closely, said there were visible tracks in the images "made by heavy machinery used in the demolition process," adding that the two buildings had been intact in early April. 

The U.N. International Atomic Energy Agency (IAEA) has repeatedly asked Iran for access to Parchin as part of a long-stalled probe into suspicions that Tehran may be seeking the ability to assemble nuclear bombs, should it decide to do so. 

The Islamic state has so far refused to let inspectors visit the facility -- which it describes as a conventional military complex -- saying there must first be a broader framework agreement on how to address the IAEA's questions. 

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The Parchin complex is at the center of Western allegations that Iran has been conducting research and experiments that could serve a nuclear weapons development programme. The Islamic Republic has repeatedly denied any such ambition. 

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Last week, the IAEA said in a report issued to member states that satellite images showed "extensive activities" at the facility southeast of Tehran. 

Western diplomats said this was an allusion to suspected cleaning at Parchin. They have earlier cited other images showing recent activity at the site, including a stream of water, as suggesting Iran is trying to remove evidence. 

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An IAEA report last November said Iran had built a large containment vessel in 2000 at Parchin in which to conduct tests that the U.N. agency said were "strong indicators of possible (nuclear) 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. 

Last week, a senior Iranian official was quoted as saying the IAEA had not yet given good enough reasons to visit Parchin. 

Reuters contributed to this report.

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DigitalGlobe satellite file image, received courtesy of the Institute for Science and International Security, showing a view of facilities within Parchin, Iran.

Updated at 8:25 a.m. ET: TEHRAN -- Iran said on Tuesday it would let U.N. nuclear investigators visit a military complex where they had been refused access to check intelligence suggesting Tehran has pursued explosives research relevant to nuclear weapons. 

Western diplomats dismissed Iran's statement as a time-buying gambit -- rather than a genuine shift toward nuclear transparency -- with Israel talking increasingly stridently of last-resort military action against its arch-enemy.

Diplomats cited a proviso in the statement saying that access to Parchin still hinged on a broader agreement on how to settle outstanding issues which the two sides have long been unable to reach -- an impasse that has put the West and Tehran on a slippery slope toward confrontation.

The West has sharpened sanctions against Iran to block its oil exports, a defiant Tehran has threatened to shut Gulf oil shipping lanes in reprisal while Israel has signaled it is losing patience with efforts to isolate the Islamic Republic.

Meanwhile, European Union foreign policy chief Catherine Ashton accepted an offer to meet Iranian nuclear negotiators to discuss Tehran's nuclear program.

Ashton represents six powers -- the United States, Russia, China, France, Britain and Germany -- in dealings with Iran, and her offer of talks came after weeks of consultations with them.

An International Atomic Energy Agency report last year said that Iran had built a large containment chamber at Parchin, southeast of Tehran, to conduct explosives tests that are "strong indicators" of efforts to develop an atom bomb.

The IAEA requested access to Parchin during high-level talks in Tehran in February, but the Iranian side did not grant it.

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"...Parchin is a military site and accessing it is a time-consuming process, therefore visits cannot be allowed frequently ... We will allow the IAEA to visit it one more time," Iran's diplomatic mission in Vienna said in a statement, according to ISNA.

It did not give a date for such a visit. Iranian diplomats and IAEA officials were not immediately available for comment.

Western suspicions about activities at Parchin date back to at least 2004, when a prominent nuclear expert assessed that satellite images showed it might be a site for research and experiments applicable to nuclear weapons.

IAEA inspectors did in fact visit Parchin in 2005 but did not see the place where the U.N. watchdog now believes the explosives chamber was built.

The IAEA named Parchin in a detailed report in November that lent independent weight to Western fears that Iran is working to develop an atomic bomb, an allegation Iranian officials deny.

Agency chief Yukiya Amano said on Monday Iran has tripled its monthly production of higher-grade enriched uranium and the U.N. nuclear watchdog had "serious concerns" about possible military dimensions to Tehran's atomic activities.

Israel-U.S. differences
The different announcements and diplomatic moves came as President Barack Obama and Israeli Prime Minister Benjamin Netanyahu ended two days of public posturing on Iran without appearing to make much progress. Obama wants Israel to refrain from attacking Iran now, and Netanyahu pointedly refused to make that promise.

At the start of their White House meeting Monday morning, Obama and Netanyahu tried to present a united front on the threat emanating from Iran. The U.S. leader reaffirmed that he would resort to military force, if necessary, to keep Iran from getting a bomb and said the U.S. "always has Israel's back where Israel's security is concerned."

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But the two men were unable to plaster over differences on how urgently military force might be needed.

Obama never made a direct, public appeal to Israel's visiting leader, but his message was clear.

"We do believe that there is still a window that allows for a diplomatic resolution to this issue," Obama said before the two-hour meeting with Netanyahu in the Oval Office.

Netanyahu thanked Obama for acknowledging that Israel will make its own choices but, for the second time in two days, ignored the American president's appeal to give diplomacy and sanctions time to percolate. Instead Netanyahu emphasized Israel's right to defend itself militarily and suggested he would not be swayed from going it alone if he thought Israel had to move faster to protect itself.

The very purpose of the Jewish state, he told Obama, is "to restore to the Jewish people control over our destiny," he said.

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Reuters and The Associated Press contributed to this report.