UN inspectors have visited the site of a nearly completed Iranian nuclear reactor for the first time in a year, foreign diplomats have said.

Inspectors from the International Atomic Energy Agency (IAEA) visited the Arak reactor in central Iran last week after the Iranian government lifted a ban, the diplomats, who asked to remain anonymous, said on Friday.

They said Iranian authorities also agreed to allow the IAEA to expand its monitoring operations of the Arak reactor.

The diplomats said Iran also agreed to grant UN inspectors greater monitoring rights at Natanz, another uranium enrichment site.

"The containment and surveillance measures were updated as the agency wanted," one of the diplomats told the AFP news agency.

The IAEA declined to comment on the reports.

Western concerns

The 40 megawatt heavy-water Arak reactor produces material for nuclear fuel that can then be further enriched to provide fissile material for weapons.

Tehran says the reactor will make isotopes purely for agricultural and medical purposes, but Western powers remain concerned that the plant could be used as part of a nuclear weapons programme.

Iran has repeatedly denied the claims and has defied UN Security Council sanctions by continuing to enrich uranium.

The US has given Iran until the beginning of the UN General Assembly meeting in late-September to agree to direct talks.

The five permanent members of the UN Security Council - the US, France, Britain, Russia and China - and Germany have also made offers of dialogue to Iran over its nuclear programme.