The UN nuclear watchdog, the International Atomic Energy Agency (IAEA) has accused Iran for the first time of building nuclear weapons.

In a leaked report, the IAEA says that credible evidence existed that Iran had carried out activities solely related to the construction of a nuclear weapon. Evidence included the construction of a large metal chamber at a military site for nuclear-related explosives testing.

The IAEA also found material that showed a detailed design for a nuclear device, as well as research on how to engineer enriched uranium into an explosive core. Other information showed that Iran built a large explosives vessel at the Parchin military complex south-east of Tehran to conduct hydrodynamic experiments, which are “strong indicators of possible weapon development”.

Iran attacked the report, maintaining it is enriching uranium solely for peaceful purposes.

The report also shows that Iran has experimented on detonator development to set off a nuclear charge. The detonation devices produced by Iran were more likely to be used in a “Fat Boy” type nuclear bomb, such as that used by the United States at Nagasaki in 1945.

“The development of safe, fast-acting detonators and equipment suitable for firing the detonators is an integral part of a programme to develop an implosion type nuclear device,” the report says.

The IAEA says Iran also has a secret project, known as the Green Salt Project that involves developing and testing high explosives used in a nuclear weapon. The IAEA report is based on eight years research and collected evidence. The main focus of Iran’s nuclear plans is to redesign and miniaturise the Pakistani nuclear weapon design by using front companies and foreign experts.

The report will heighten international pressure on Iran. Last week, the UK government said it would assist the US if it chose to carry out military strikes at key Iranian facilities (MEED 8:9:11).

Russia has also warned against potential Israeli military action, saying it would be “a very serious mistake fraught with unpredictable consequences”, according to Russian Foreign Minister Sergei Lavrov.