"A team of IAEA inspectors today carried out an inspection at Parchin, including the taking of environmental samples," spokesman Mark Gwozedecky said.

IAEA chief Mohamed ElBaradei announced last week that Iran had finally given the green light for his inspectors to probe Parchin after seeking access to the site since July.

Environmental samples are swipes taken to check for radiation. Results from the highly sensitive sampling, which can detect miniscule amounts of radioactive particles even if a site has been cleaned, are available after about a month of laboratory analysis.

Iran had warned Wednesday that it would not tolerate "spying" at the Parchin facility.

"We have allowed inspections into our military installations but we will not allow any espionage or the theft of information from our military sites," Hossein Mousavian, the spokesman for Iran's nuclear negotiations team, told the conservative Mehr news agency.

"It is not necessary for the inspectors to enter the installations. They are authorized to take samples outside (the buildings) using their equipment."

But a diplomat close to the IAEA said the one-day Parchin inspection "went as planned" and that inspectors had been inside buildings they wanted to see.

"There was no restriction of any kind" in the area where the IAEA inspectors were, the diplomat said.

Iran was allowing the IAEA visit as a confidence-building measure after it resumed talks this week in Brussels with the European Union on a trade accord, 18 months after negotiations were suspended due to concerns about Tehran's nuclear plans.

The negotiations on a trade and cooperation agreement were restarted after Iran agreed to suspend uranium enrichment, the crucial part of the nuclear fuel cycle which can also make material for atomic bombs, in an accord thrashed out following intense pressure notably from the United States, which says Iran is secretly developing nuclear weapons.

But the resumption was clouded by a reported announcement from Tehran that Iran plans to resume uranium enrichment soon.

Iran has consistently claimed it is only giving up enrichment voluntarily to build confidence and reserves the right to enrich uranium when it wishes since its nuclear program is a peaceful effort geared to making electricity.

Tehran gave permission for inspectors to take environmental samples from the massive Parchin site, located around 30 kilometers (20 miles) southeast of Tehran, in order to disprove the US allegations of secret weapons-related activities.

Washington has voiced concern that the Iranians may be working on testing high-explosive charges with an inert core of depleted uranium at Parchin as a sort of dry test for how a bomb with fissile material would work.

A US official told AFP earlier this month that the testing in Parchin may "amount to (nuclear) weapons intent".

Tehran has strongly denied carrying out any nuclear-related work at the site.

Parchin is an example of a so-called "transparency visit" where the IAEA is going beyond its mandate under the nuclear Non-Proliferation Treaty (NPT) to check if nuclear materials have been diverted away from peaceful use. There may be no nuclear materials there if only depleted uranium is being used.

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