It is very likely that all the roughly 15,000 centrifuges operating at Iran's biggest uranium enrichment plant at Natanz were badly damaged or destroyed because of a power cut caused by an Israeli strike, the U.N. nuclear watchdog chief told the BBC on Monday.

The IAEA says radiation levels outside the Natanz and Isfahan facilities remain normal following Friday's Israeli strikes.

Rafael Grossi says while buildings above ground in Natanz have been destroyed, strategic locations underground have not been struck