WHAT IS KNOWN ABOUT HIM

Western officials and experts believe Dr Mohsen Fakhrizadeh played a pivotal role in suspected Iranian work in the past to develop the means to assemble a nuclear warhead behind the facade of a declared civilian uranium enrichment programme.

He lived in the shadows under high security and was never made available to United Nations nuclear investigators. Iran acknowledged his existence but denied that he was involved in the nuclear programme.

The assassinations of four Iranian scientists associated with the nuclear programme between 2010 and 2012 may have stiffened Teheran's resolve not to give the International Atomic Energy Agency access to Dr Fakhrizadeh - for fear this could lead to information about him and his whereabouts leaking. Dr Fakhrizadeh was also believed to have been involved in Iran's ballistic missile development.

HIS BACKGROUND

Born in 1958 in Qom, Dr Fakhrizadeh was believed to be a deputy defence minister and a Revolutionary Guards Brigadier-General. He also holds a nuclear engineering doctorate and taught at Iran's University of Imam Hussein.

WHO THE OTHER MURDERED NUCLEAR SCIENTISTS ARE

Assassins have targeted five other Iranian nuclear scientists before. Dr Mostafa Ahmadi Roshan, 32, and Dr Majid Shahriari were killed in 2012 and 2010 respectively, by a magnetic bomb attached to their cars in Teheran.

Dr Mostafa was an expert in making polymeric membranes for gaseous diffusion, part of the process needed for the enrichment of uranium, The Guardian reported.

Dr Masoud Alimohammadi, a quantum field theorist, was killed in January 2010 by a booby-trapped motorcycle parked in front of his house. In July 2011, Dr Darioush Rezaeinejad, an academic, was shot dead by gunmen riding on motorcycles.

Dr Fereidoon Abbasi Davani, Iran's former atomic chief, survived an attack by assailants on motorcycles. Analysts have said the assassinations were aimed at disrupting Iran's nuclear programme, which has since suffered a series of setbacks.

REUTERS