It also outlined further advances at a reactor under construction at Arak which Western countries fear could provide Iran with plutonium if the fuel is reprocessed.
Highly enriched uranium and plutonium can both be used in the explosive core of a nuclear weapon. Iran has denied this is its aim.
The IAEA report, seen by AFP, said Iran has installed at Natanz almost 700 IR-2m centrifuges and/or empty centrifuge casings, compared with just 180 in February.
Iran has said it intends to install around 3,000 of the new centrifuges at Natanz — where around 13,500 of the older models are installed — enabling it to speed up the enrichment of uranium.
The UN Security Council has passed numerous resolutions calling on Iran to suspend all enrichment and heavy water activities — the kind being built at Arak –, and has imposed four rounds of sanctions.
Last year additional unilateral US and EU sanctions targeting Iran’s oil exports and its financial system began to cause real problems for the Persian Gulf country’s economy.
Diplomatic efforts to resolve the impasse, most recently in six-power talks with Iran in Kazakhstan in April and last week between Iran and the IAEA, have failed to make concrete progress.