The US has rejected allegations by Iran that it had a hand in a bomb attack that killed an Iranian nuclear scientist.
Iran's foreign ministry accused US and Israeli 'mercenaries' of being behind the bomb plot.
However, State Department spokesman Mark Toner said the charges of US involvement were 'absurd'.
Massoud Ali Mohammadi, a particle physics professor at prestigious Tehran University, died when a bomb strapped to a parked motorcycle was triggered by remote control outside his home in northern Tehran.
Tehran's foreign ministry spokesman Ramin Mehmanparast was quoted in Iranian media as seeing 'signs of evilness by the triangle of the Zionist regime, America and their mercenaries in Iran in this terrorist incident'.
However, he said that Iran would not be deterred from its nuclear efforts, which have attracted much controversy in the West.
'Such terrorist acts and the physical elimination of the country's nuclear scientists will certainly not stop the scientific and technological process but will speed it up,' he said.
Iran's chief prosecutor also implicated US and Israeli intelligence services in the bombing that killed the nuclear scientist.
'Given the fact that Massoud Ali Mohammadi was a nuclear scientist, the CIA and Mossad services and agents most likely have had a hand in it,' Abbas Jafari Dolatabadi told state media.
