UN nuclear experts yesterday inspected a uranium enrichment site whose existence was announced by Iran last month, the semi-official Mers news agency said.

Tehran's secrecy about the site, which diplomats say was detected by western intelligence three years ago, has raised fears it is running a covert programme to develop nuclear bombs. Iran, which says it is seeking only to generate electricity, agreed to open up the plant to the International Atomic Energy Agency (IAEA) at talks with six world powers on October 1.

"The inspectors... visited the facility in central Iran. They are expected to visit the site again," Mehr news agency reported, without giving a source. There was no immediate confirmation from the IAEA.

The IAEA inspectors arrived in Iran early yesterday to examine the site, under construction 160 kilometres south of Tehran. It is Iran's second site for enriching uranium, which can be used to fuel power plants or to provide material for bombs.

In talks with world powers, Iran also promised to send abroad much of its enriched uranium reserve for processing into fuel for a reactor that makes radio-isotopes for medical care.

World powers regard both steps as tests of Iran's stated intent to use enriched uranium only for civilian purposes and a basis for follow-up talks on curbing enrichment itself, which would bring Iran trade and technology rewards in return.

The proposal that Iran send enriched uranium abroad is also seen as a way of reducing its stockpile below the threshold needed to produce fissile material for a bomb.