Iranian nuclear scientist and university professor, Mostafa Ahmadi-Roshan, was killed when his car exploded in North Tehran. The Iranian authorities blamed Israel for what it called a "terrorist bomb blast." Ahmadi-Roshan was a chemistry engineer and department supervisor at the Nantz uranium enrichment facility, one of two sites where scientists are suspected to be working to advance nuclear weapons technology. Witnesses said the blast occurred after an unidentified motorcyclist stuck a magnetic explosive device to the car, which injured at least two others. This is the fourth such attack in the past two years for which Iran has implicated Israel and the United States for attempting to assassinate key figures involved in the nuclear program, but the countries deny responsibility.