"Today, we went to Lavizan, we took environmental samples, we did all we wanted to. We got a prompt response for access from the Iranians," International Atomic Energy Agency (IAEA) director general ElBaradei told AFP.

ElBaradei, who is in Moscow for a conference on the peaceful use of nuclear energy, said the IAEA inspectors had seen "relevant equipment and they will be going to another site tomorrow to see more equipment."

He refused to say specifically what equipment was involved. But there have been reports that commercial satellites have detected a radiation body counter machine at the site in Lavizan Shiyan, a Tehran neighbourhood, where the Iranians have torn down buildings and removed topsoil.

"I think we got prompt access and I'm pleased with the prompt access. We did all we wanted to do," said ElBaradei, who at an IAEA meeting earlier this month had criticized the Iranians for giving "less than satisfactory" cooperation in helping the IAEA answer US charges that Iran is secretly developing nuclear weapons.

Iran has since then said it will resume making centrifuges for uranium enrichments that could produce bomb-grade atomic material, drawing sharp criticism from ElBaradei, as well as the United States and the European Union, for lack of cooperation.

Diplomats confirmed to AFP a report that the IAEA had received information about concealment activity detected by the US commercial firm DigitalGlobe's Quickbird satellite at an alleged nuclear site in Lavizan Shiyan.

In August 2003, satellites showed large buildings inside a large perimeter.

In March 2004, another satellite pass showed that buildings had been removed, roads and walkways removed or covered and the earth scraped.

The Washington ISIS think tank said on its website that this set off alarm bells "because it is the type of measure Iran would need to take if it was trying to defeat the powerful environmental sampling capabilities of IAEA inspectors."

The site was brought to public attention in May last year, when an Iranian opposition group, the National Council of the Resistance of Iran, alleged that it was home to a biological weapons research facility.

The United States claims that Iran is hiding an atomic weapons program and has urged the IAEA to cite Tehran before the UN Security Council for possible sanctions.

The 35-nation board of the IAEA passed a resolution on June 18 rebuking Tehran for failing to come clean about its nuclear program, deploring its lack of cooperation and calling for the investigation into Iran's nuclear activities to be wrapped up within a few months.

Iran confirmed Sunday it had razed the Lavizan site but insisted it was to make a park and not to cover up nuclear weapons activities as the United States has alleged.

"The municipality wanted to make a park, but there was a dispute with the defence ministry," top national security official Hassan Rowhani was quoted as saying by the official news agency IRNA.

"The land belonged to the municipality" and the building was demolished, Rowhani insisted, adding that "we have nothing to hide."

On June 17, the United States accused Iran of razing nuclear sites to hide banned nuclear activity.

"It's deplorable but not surprising that Iran's deception has gone to the extent of bulldozing entire sites to prevent the IAEA from discovering evidence of its nuclear weapons program," said US State Department spokesman Richard Boucher.

Iranian officials dismissed the allegations, and said inspectors from the IAEA, the UN nuclear watchdog, were welcome to visit.

"The United States is making a psychological war against Iran. We cannot forget that the US went to war against Iraq because of weapons of mass destruction but has not found any," Asefi said.

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