Shahram Amiri was allegedly interrogated by CIA for over a year before his release in July 2010 [GALLO/GETTY]

26 January 2007: Ardeshir Hassanpour, a nuclear scientist working at Iran's uranium conversion plant in Isfahann, dies. Officials blame his death on unexplained gas poisoning.

June 2009: Shahram Amiri, who worked for Iran's atomic energy organisation, disappears during a pilgrimage (Oumra) to Mecca. He surfaces a year later in July 2010, claiming he had been abducted by CIA agents.

12 January 2010: Massoud Ali Mohammadi, a leading scientist, was killed when a remote-controlled bomb exploded near his car.

29 November 2010: Dr. Majid Shahriari,  member of the nuclear engineering department of Shahid Beheshti University in northern Tehran, killed by a remote-controlled car bomb. Dr. Fereydoon Abbasi, a nuclear physics researcher at the defence ministry, was injured in a similar but separate explosion on the same day.

Source: Al Jazeera