VIENNA, Sept 21 (Reuters) - Iran has begun tests on a facility that will produce a large amount of material for nuclear centrifuges, a top Iranian nuclear official said on Tuesday.

Gholamreza Aghazadeh, the head of Iran's Atomic Energy Organisation, told reporters in Vienna Iran had begun converting 37 tonnes of raw uranium into material which is fuel for nuclear centrifuges -- the machines that enrich uranium.