Iran has denied reports it had tried to clean up suspicious activities at the controversial Parchin military complex outside the capital, Tehran, ahead of a planned United Nations inspection.

The Islamic Republic dismissed on Thursday the allegations published by a US-based non-proliferation think-tank as part of an effort to kill the nuclear deal it signed with six world powers on July 14.

In a statement, Iran's UN mission said opponents are carrying out a "vicious" campaign "to poison the positive environment at the global level" and derail the agreement. 

It's important not to overreact and wait to have conclusive answers to each allegation.

Ariane M. Tabatabai, Nuclear and security expert, Georgetown University

"These claims are preposterous and the repetition of the similar unfounded claims that reappear from time to time and have been disproved each time," the statement said.

On Wednesday, the Washington-based Institute for Science and International Security said satellite images showed "renewed activity at a site" inside Parchin, which the West has suspected of being used for nuclear activities.

The nuclear non-proliferation group said the images, taken after the Vienna deal was announced, raised "obvious concerns that Iran was conducting further sanitisation efforts to defeat" verification by UN's International Atomic Energy Agency (IAEA).

A separate report published in the US news site Bloomberg, also made similar allegations and quoted US Congress members as saying that the activities at Parchin, "calls into question Iran's intention" to comply with the landmark agreement.

'Nothing new'

Iran's UN mission, however, called the reports as "baseless", adding that construction work at the military complex, which also includes offices and residential buildings, is "quite normal".

It said "extensive construction works have been underway to repair the road" running opposite a dam near Parchin.

"These works required the use of heavy bulldozers and other heavy construction machinery in the area."

A photo provided by Institute for Science and International Security was presented as evidence of "sanitasion" efforts by Iran to "defeat verification" by the IAEA.

Ali Vaez, senior Iran analyst at the International Crisis Group, told Al Jazeera that the new satellite images "reveal nothing new" about Parchin.

He said that construction and renovation have been going on at the site before IAEA requested to carry out a third inspection in 2011. The third inspection has yet to take place. Two inspections were carried out in 2005.

But he said that the reports "provide ammunition for the opponents of the deal, without enhancing our insights into Iran's past nuclear activities".

Vaez said that even if IAEA gets immediate and full access to Parchin, and fail to find any trace of nuclear material, "detractors will take it as proof of Iranian deception".

"If access is denied, they will see it as another sign of Iranian obfuscation," he said.

"Parchin's puzzle might remain unresolved. But what matters is that the nuclear agreement ensures that there will be no more Parchins in the future," Vaez said.

Ariane M Tabatabai, a nuclear expert and visiting professor at Georgetown University, Washington DC, told Al Jazeera that similar reports are likely to surface as the implementation of the nuclear deal moves forward.

Impact of nuclear deal on Iran

"It's important not to overreact and wait to have conclusive answers to each allegation," she said, adding that it is up to the IAEA to determine the facts on the ground.

Tabatabai said that the latest report could reinforce the idea among undecided members of the US Congress "that Iran is not to be trusted" to vote against the deal.

Still, she said that the deal will move forward, adding that "the cost of failing at this stage is too high" especially for the US, which stands to lose more credibility abroad.

On Wednesday, US President Barack Obama delivered a speech urging members of Congress to support the deal, warning that a rejection of the deal could lead to war.

Source: Al Jazeera