This week's assassination of an Iranian scientist was carried out in a "Zionist style", President Mahmoud Ahmadinejad said on Thursday, in his first direct comment on the bombing attack in Tehran.
Iranian officials and media have blamed both Israel, which Tehran calls "the Zionist regime", and the United States for Tuesday's killing of professor Massoud Ali-Mohammadi. Washington has dismissed the charge of US involvement as absurd.
"The depth of the enemies' grudge can be seen in the university professor's assassination," Ahmadinejad said, ISNA news agency reported.
"The manner of bomb planting shows a Zionist style and they want to make sure that Iran would not advance," he said.
State media have said Ali-Mohammadi was killed by a remote controlled bomb strapped to a motorcycle. He was buried in Tehran on Thursday, with the crowd chanting "Death to America" and "Death to Israel", state television reported.
Iranian officials have described the slain professor as a nuclear scientist, but a spokesman said he did not work for the Atomic Energy Organisation at the center of the Islamic Republic's disputed nuclear program.
"They don't want to see thinkers and scientists in Iran and do not want to see its development," Ahmadinejad said, referring to Iran's foes, IRNA news agency reported. "The enemies can not take away the concept of genius from Iran by killing geniuses."
Tuesday's bombing, a rare attack in the Iranian capital, occurred at a time of heightened tension in the Islamic state, seven months after a disputed presidential election plunged the major oil producer into turmoil.
It also coincided with a sensitive time in Iran's row with the West over its nuclear ambitions, with major powers expected to meet soon to discuss possible new sanctions on Tehran over its refusal to halt its atomic work.
The West suspects Iran's nuclear work is aimed at developing bombs. Tehran says it seeks only to generate electricity.
State media described Ali-Mohammadi as a "committed and revolutionary" professor, suggesting he backed the government.
But an opposition website, Jaras, said he was an opposition supporter who backed moderate candidate Mirhossein Mousavi in last June's disputed election, which plunged Iran into turmoil.