The UN nuclear agency has said it is "increasingly concerned" about intelligence suggesting that Iran continues to secretly work on developing a nuclear payload for a missile and other components of a nuclear weapons programme.
The International Atomic Energy Agency (IAEA) report said "many member states" are providing evidence for the assessment, describing information as "credible, extensive and comprehensive".
The report was made available after being shared with the 35 IAEA member nations and the UN Security Council. It also said Tehran has fulfiled a promise made earlier this year and started installing equipment to enrich uranium at a new location – an underground bunker better protected from air attack.
Enrichment can produce both nuclear fuel and fissile warhead material, and Tehran – which says it wants only to produce fuel with the technology – is under four sets of UN Security Council sanctions for refusing to freeze it.
Tehran also denies secretly experimenting with a nuclear weapons programme.