Inspectors from the UN nuclear agency have arrived in Tehran to visit a nuclear facility that has long been off-limits to outside experts.

Two inspectors from the International Atomic Energy Agency will visit the heavy-water production plant in the central city of Arak today. Iran agreed last month with the IAEA to allow expanded UN monitoring at nuclear sites.

That agreement was not part of the deal Iran struck last month with world powers that commits Tehran to freeze its nuclear programme for six months to get limited relief from economic sanctions.