Vienna  - Iran still needs to provide substantive explanations on questions regarding alleged nuclear weapons studies, the International Atomic Energy Agency
(IAEA) said Monday.

The weaponization issues regarding uranium conversion, high explosives testing and design of a missile re-entry vehicle remain a "matter of serious concern," the UN nuclear watchdog said, adding that Tehran insisted the allegations were based on fabricated data.

Iran continued to defy UN Security Council demands to halt uranium enrichment and is currently operating around 3,500 centrifuges. By the end of summer, Iran plans to install 6,000 centrifuges, senior UN diplomats said. (dpa)