UN nuclear inspectors arrived in Tehran Tuesday to visit Iran's Gachin uranium mine for the first time in several years, Atomic Energy Organisation Behrouz Kamalvandi said.

"These three inspectors are scheduled to travel tomorrow to Bandar Abbas province to visit the Gachin mine," Kamalvandi was quoted by state news agency IRNA as saying.

The scope of the visit "will be only to the extent of what they need (to know)," said Kamalvandi, referring to "managed access" to the mine that is among six steps of a framework deal reached with the UN atomic watchdog in November.

As part of the first phase of the deal, UN experts visited the heavy water plant at the unfinished Arak reactor on December 8, when all of the International Atomic Energy Agency's (IAEA)"technical objectives" were met, the Vienna-based agency said.

The Arak reactor, still under construction, is a major source of concern for Western powers, who fear the plutonium it will produce as a by-product could provide Iran with an alternative route to an atomic bomb.

The deal also allows UN experts to visit Gachin -- which has been off-limits to them since 2005.

As it stands, Iran is only obliged to inform the IAEA three months before it transfers fissile material into a nuclear facility.

Iran also reached a landmark deal in November with the so-called P5+1 group -- the United States, China, Russia, Britain, France and Germany -- on its disputed nuclear drive, which the West suspects has military dimensions, despite Tehran's denial.