VIENNA: Iran has started the process of enriching uranium to 60% fissile purity at its above-ground Pilot Fuel Enrichment Plant at Natanz, the UN nuclear watchdog said on Saturday, confirming earlier statements by Iranian officials. "The Agency today verified that Iran had begun the production of UF6 enriched up to 60% U-235 by feeding UF6 enriched up to 5% U-235 simultaneously into two cascades of IR-4 centrifuges and IR-6 centrifuges at the Natanz Pilot Fuel Enrichment Plant," the International Atomic Energy Agency said in a statement. UF6 is uranium hexafluoride, the form in which uranium is fed into centrifuges for enrichment.