"We categorically deny any nuclear-related testing at Parchin," a huge military complex 30 kilometres (19 miles) southeast of Tehran, Hossein Mousavian, head of Iran's delegation to a meeting of the UN atomic agency in Vienna, told AFP.

A senior US official told AFP the United States was concerned about high-explosives testing in Parchin that may be nuclear-related and "amounts to weapons intent".

Mousavian also denied reports that the International Atomic Energy Agency had asked to visit Parchin as part of its investigation of Iran's nuclear program.

"They did not request to go," he said.

He said that "if this is requested by the IAEA, we are fully ready to cooperate."

Mousavian said the IAEA had asked Iran "four weeks ago about reports from open sources of explosive testing but they did not mention Parchin."

Diplomats have told AFP, however, that the IAEA had asked to visit Parchin and that the Iranians have not agreed to the visit.

Parchin is a site for a variety of defense projects, including Defense Industries Organization (DIO) work in chemical explosives, but the IAEA is wondering if Tehran may be working on nuclear weapons work there.

Iran maintains that its nuclear program is strictly civilian and peaceful and that it is not developing atomic weapons.

A diplomat close to the IAEA confirmed that the agency had asked to send inspectors to Parchin but said this was not included in an IAEA report on Iran published September 1 since "whenever you are in the negotiating process, you should not mention what you are negotiating.

A Western diplomat close to the IAEA said however that the sudden spurt over Parchin was suspect, as it came just as the IAEA board of governors was meeting on Iran.

"Why every time there is a board meeting, there is a new suspect site," the diplomat said, hinting that this was part of a US-orchestrated campaign to rally opinion against Iran.

A US official had told AFP last week that the IAEA had, according to verbal accounts, dropped the mention of Parchin in a written repport on Iran published on September 1, as well as a reference to concern about Iran's work with beryllium.

Beryllium has civilian applications but can also be used in combination with polonium to make a neutron initiator that is effectively a trigger for a nuclear bomb.

The official said the concern about Parchin was that the Iranians may be working on testing "high-explosive shaped charges with an inert core of depleted uranium" as a sort of dry test for how a bomb with fissile material would work.

A non-American diplomat confirmed the US assertion.

An IAEA spokesman refused to comment.

A US think tank with ties to the diplomatic and intelligence communities late Wednesday released seven satellite photographs of Parchin, arguing the new evidence warranted international inspections.

The pictures, presented by the Institute for Science and International Security along with ABC News, show a large industrial complex hidden in a warren of valleys and crevices created by a mountainous plateau in northern Iran.

A paved road snaking in between barren hills connects warehouse-like buildings and smaller installations.

But expert commentary accompanying the material suggests that the Parchin conventional weapons complex could also be used for nuclear work.

"This site is a logical candidate for a nuclear weapons-related site, particularly one involved in researching and developing high explosive components for an implosion-type nuclear weapon," weapons experts David Albright and Corey Hinderstein commented on the images.

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