Iran said on Saturday that it has evidence Washington and Britain were behind the latest assassination of one of its scientists, FNA reported.
In the fifth attack of its kind in two years, a magnetic bomb was attached to the door of 32-year-old Mostafa Ahmadi Roshan Behdast's car during the Wednesday morning rush-hour in the capital. His driver was also killed.
Iran sent a letter to the Swiss embassy in Tehran, saying that CIA-led operations in the Islamic Republic are known, and blaming the US for supporting "terrorist groups against Iran".
"We have reliable documents and evidence that this terrorist act was planned, guided and supported by the CIA," the Iranian foreign ministry said in a letter handed to the Swiss ambassador in Tehran.
"The documents clearly show that this terrorist act was carried out with the direct involvement of CIA-linked agents."
The Swiss Embassy has represented US interests in Iran since Tehran and Washington cut diplomatic ties shortly after the 1979 Islamic Revolution.
A letter of condemnation was also sent to the British government, saying the killing of Iranian scientists "started exactly after chief of the British Secret Intelligence Service John Sawers declared the beginning of intelligence operations against Iran".
Iran demanded a response from both governments.
Roshan Behdast was the fifth Iranian scientist assassinated since 2007. The Wednesday blast took place on the second anniversary of the martyrdom of Iranian university professor and nuclear scientist, Massoud Ali Mohammadi, who was also assassinated in a terrorist bomb attack in Tehran in January 2010.
The assassination method used in the Wednesday bombing was similar to the 2010 terrorist bomb attacks against the then university professor, Fereidoun Abbassi Davani - who is now the head of Iran's Atomic Energy Organization - and his colleague Majid Shahriari. Abbasi Davani survived the attack, while Shahriari was martyred.
Another Iranian scientist, Dariush Rezaeinejad, was also assassinated through the same method on 23 July 2011.
Iran has blamed the CIA, MI6 and the Israeli Mossad agency for the terror attacks on the lives of its scientists.
Israeli Defense Forces (IDF) Chief of General Staff Benny Gantz said Tuesday that 2012 would be a critical year regarding Iran and that there may be more "unnatural" events that happen to them.
"2012 will be a critical year in the connection between Iran gaining nuclear power, changes in leadership, continuing pressure from the international community and events that happen unnaturally," he said.