Satellite images have revealed that Iran is developing a second way to a nuclear weapons capability by operating a plant that could produce plutonium.
The activity is taking place at a heavily-guarded Iranian facility from which international inspectors have been barred for 18 months.
According to the Telegraph, the images showed that Iran has activated the Arak heavy-water production plant.
Heavy water is needed to operate a nuclear reactor that can produce plutonium, which could then be used to make a bomb.
Inspectors from the IAEA were unable to visit the facility since August 2011 and Iran has refused repeated requests for information about the site, which is 150 miles south-west of Tehran.
Western governments and the IAEA have held information about activity at Arak for some time.
But now exclusive images are the first to put evidence of that activity into the public domain, the paper said.