The International Atomic Energy Agency (IAEA) has asked Iran to explain evidence suggesting that Iranian scientists have experimented with an advanced nuclear warhead design, according to a Thursday evening report by Britain's Guardian newspaper.

Previously unpublished documentation in a dossier compiled by the UN's nuclear watchdog say Iranian scientists may have tested high-explosive components of the design known as "two-point implosion". The technology reduces the diameter of a warhead and makes it easier to put a nuclear warhead on a missile.

The dossier, "Possible Military Dimensions of Iran's Nuclear Program", includes reports submitted to the IAEA by western intelligence agencies.