Two hitmen on a motorcycle were said to have attached a magnetic bomb to the car of Mostafa Ahmadi Roshan killing him and a passenger instantly as they sat in the Iranian-assembled Peugeot 405 in the northern district of the capital Tehran.
A 32-year-old chemistry expert and director of the Natanz uranium enrichment facility in central Iran, Roshan was said to have been involved in the development of Tehran's atomic program.
The assassination had strong similarities to other executions in recent years of scientists linked to the program and underlined the belief that a major covert operation is underway against it.
Iran has accused Israel's Mossad, the CIA and Britain's spy agencies of engaging in an underground "terrorism" campaign against nuclear-related targets, including at least three killings since early 2010 and the release of a malicious computer virus that temporarily disrupted controls of some centrifuges - a key component in nuclear fuel production.
All three countries have denied the Iranian accusations.
Last week, Tehran pointed the finger at the U.S. and Israel as being behind the latest terrorist attack but promised it would not be a setback to the expanding nuclear program.
|Mostafa Ahmadi-Roshan, the target who|
was killed in Tehran when two motorcyclists
attached a magnetic bomb to his car.
First Vice President Mohammad Reza Rashimi added that Israeli agents were behind the attack, but cannot "prevent progress" in what Iran claims are peaceful nuclear efforts.
Israeli officials have hinted about covert campaigns against Iran without directly admitting involvement.
Previously, Israeli military chief Lt. Gen. Benny Gantz told a parliamentary panel that 2012 would be a "critical year" for Iran - in part because of "things that happen to it unnaturally."
Roshan, a graduate of the prestigious Sharif University of Technology in Tehran, was deputy director of commercial affairs for the Natanz uranium enrichment plant and in charge of purchasing and supplying equipment for the facility.
Natanz is Iran's main enrichment site.
The U.S. and its allies are pressuring Iran to halt uranium enrichment, a key element of the nuclear program that the West suspects is aimed at producing atomic weapons.
Uranium enriched to low levels can be used as nuclear fuel but at higher levels, it can be used as material for a nuclear warhead.
Iran denies it is trying to make nuclear weapons, saying its program is for peaceful purposes only.
Since December, Iran has held or announced a series of war games that included threats to close the Gulf's vital Strait of Hormuz - the passageway for about one-sixth of the world's oil - in retaliation for stronger U.S.-led sanctions.
"Assassinations, military threats and political pressures ... The enemy insists on the tactic of creating fear to stop Iran's peaceful nuclear activities," lawmaker Javad Jahangirzadeh said after the blast.
"Instead of actually fighting a conventional war, Western powers and their allies appear to be relying on covert war tactics to try to delay and degrade Iran's nuclear advancement," said Theodore Karasik, a security expert at the Dubai-based institute for Near East and Gulf Military Analysis.
He said the use of magnetic bombs bears the hallmarks of covert operations.
|Type 45 Destroyer HMS Daring was sent to the Strait of Hormuz by the|
British Navy after Iran threatened to block it because of attacks on its