* IAEA believes Iran held nuclear-relevant tests at Parchin
* Iran says it is a conventional military facility
* Western diplomats suspect Iran is cleaning up site
By Fredrik Dahl
VIENNA, Nov 21 (Reuters) - Iran has been hauling dirt to a military site U.N. nuclear inspectors want to visit, Western diplomats said on Wednesday, saying the findings were based on satellite images and they reinforced suspicions of a clean-up.
They said the pictures, presented during a closed-door briefing for member states of the International Atomic Energy Agency (IAEA), suggested Iran was continuing to try to hide incriminating traces of any illicit nuclear-related activity.
The allegations come a few days after the IAEA said in a report on Iran that "extensive activities" undertaken at the Parchin site since early this year would seriously undermine its inquiry, if and when inspectors were allowed access.
Iran has so far denied the agency's request for a visit.
The U.N. agency believes Iran may have conducted explosives tests that could help develop nuclear weapons at Parchin and wants immediate access to investigate the facility. Iran denies this, saying Parchin is a conventional military complex.
The latest satellite image, dated Nov. 7, showed what appeared to be piles of dirt, according to diplomats who attended the briefing by chief U.N. inspector Herman Nackaerts.
"They have been scraping the earth. Now they obviously want to put down new earth. There are piles of them that you can see," one diplomat said, adding a fence had also come down.
"We are wondering whether they are intending to bring down ... the buildings, we don't know yet," he added, referring to a structure believed to house a steel chamber for past explosives tests, as well as a nearby building.
Iran's mission to the IAEA was not available for comment.
The IAEA report, issued on Friday, listed activities observed at Parchin since February, including the removal of "considerable quantities" of earth at the location in question and its surrounding area, which it said covered 25 hectares (62 acres).
This had been followed by "further removal of earth to a greater depth ... and the depositing of new earth in its place."
Earlier IAEA reports have described the demolition of several smaller buildings at Parchin and other apparent clean-up work. The building where the IAEA believes the tests were carried out has been covered up, it says.
Iran denies Western accusations that it is seeking to develop the capability to make nuclear bombs.
But U.N. inspectors suspect that research and experiments relevant to nuclear weapons development have been conducted in the past, and possibly continues.
IAEA chief Yukiya Amano has pressed Iran to allow his inspectors to go to Parchin, a sprawling facility southeast of the capital Tehran. The IAEA also wants access to other sites, as well as to officials and documents.
"There are lots of activities (at Parchin) since the beginning of this year and some of these activities are quite important," Amano said during a visit to Paris this week, referring to the apparent sanitisation efforts.
Tehran says it must first reach a broader agreement with the IAEA on how the Vienna-based U.N. agency should conduct its investigation into alleged nuclear bomb research in the Islamic state before it can possibly be allowed to visit Parchin.
A series of meetings this year between the IAEA and Iran, the most recent in August, has failed to make progress in allowing the U.N. agency to resume its long-stalled inquiry.
The two sides will meet again on Dec. 13 but Western diplomats say they are not optimistic about any breakthrough.
The IAEA's talks with Iran are separate from - but are still closely linked to - efforts by six world powers to diplomatically resolve the decade-long nuclear dispute with Iran that has raised fears of a new war in the Middle East.
In Brussels on Wednesday, the six powers - the United States, France, Germany, Britain, Russia and China - said they were committed to holding a new round of negotiations with Iran as soon as possible.