The UN atomic watchdog has confirmed that Iran's partial nuclear freeze, part of a landmark deal with world powers struck in November, began on Monday as planned.
The International Atomic Energy Agency said in a report passed to member states that Iran "has ceased enriching uranium above five percent" fissile purities at the Natanz and Fordo facilities.
The report, seen by AFP, said that Iran was also converting its stockpile of medium-enriched uranium, a particular concern to the international community since it can be relatively easily be further purified to weapons-grade.
It added that Iran "is not conducting any further advances to its activities" at Natanz, Fordo or the heavy-water reactor under construction at Arak, which could in theory provide Iran with weapons-grade plutonium.
In addition, Iran "is continuing to construct" a plant for the conversion of low-enriched uranium needed to ensure that its reserve of this material does not grow during the next half-year, the IAEA report said.
"It's all fine, all their requirements have been fulfilled," one diplomat told AFP. A second said: "It is promising, although there is a lot of work to do" over the next six months.
Under the terms of the November 24 deal, Iran has pledged to limit enrichment to low purities for a period of six months, convert its medium-enriched uranium and not make further advances at its nuclear facilities.
The IAEA will also be given additional inspection rights, including daily visits to Natanz and Fordo and access to centrifuge workshops.
In exchange Western powers will slightly loosen crippling sanctions in a package worth between $6-7 billion, according to the White House, including $4.2 billion in frozen overseas foreign exchange assets in eight instalments starting February 1.
During the six months, Iran and the P5+1 powers -- the US, China, Russia, France, Britain and Germany -- are due to hammer out a long-term "comprehensive accord" aimed at ending once and for all the standoff over Iran's nuclear work.
This six-month period can however be extended by mutual agreement. According to the November 24 interim deal, the parties aim to conclude negotiating and begin implementing it within a year.