Iran on Monday accused US and Israeli intelligence services, the CIA and Mossad, of killing a prominent scientist in the Islamic Republic's controversial nuclear programme.
"The Zionist regime this time shed the blood of university professor Dr Majid Shahriari to curb Iran's progress," the office of President Mahmoud Ahmadinejad said in a statement posted on its website.
"Political and intelligence analysts are wondering about the link between this inhumane act and the recent remarks of chief of the British intelligence agency (MI6), who advocated hiring spies to act against Iran," it added.
MI6 chief John Sawers said in October that diplomacy was not enough to stop Iran developing atomic weapons, and instead urged an "intelligence-led" approach to stopping nuclear proliferation.
Iran's Interior Minister Mostafa Mohammad Najjar also accused the CIA and Mossad of the attacks, state television reported.
"Mossad and the CIA are the enemies of Iranians and always seek to hurt this nation. They particularly want to stop our scientific progress," he said, after state media reported Shahriari was killed and another nuclear scientist wounded in separate attacks in the capital.
"The desperate terrorist act against the two academics shows their weakness and inferiority," he said of Monday's attacks in which assailants on motorbikes reportedly attached bombs to the scientists' cars on their way to work.
Western governments suspect Iran's nuclear programme masks a drive for atomic weapons capability, an ambition Tehran has steadfastly denied.