A bomb which exploded in north Tehran, killing Dr Moussad Ali-Mohammadi, a professor of nuclear physics, has prompted competing theories on which was of greater significance: his academic work or his support for the opposition? Alongside official allegations that the US, Israel and their allies were responsible, is evidence that Dr Ali-Mohammadi had been outspoken in his support for opposition leader Mir-Hossein Moussavi.
Who's behind the assassination of an Iranian nuclear scientist?
The Daily Telegraph reported: "An Iranian nuclear physicist with ties to the reformist movement led by the opposition leader, Mir Hossein Moussavi, has been killed by a bomb near his home.
"Dr Moussad Ali-Mohammadi was leaving his house on his way to work at Tehran University when the bomb, attached to a motorbike, went off, killing him instantly.
"The Iranian authorities said they suspected the hand of exiled opposition movements working on behalf of America and Israel, a charge denied by Washington."
A report early last year would appear to support the charge that a foreign hand lay behind the Tuesday's killing.
In February, The Daily Telegraph said: "Israel has launched a covert war against Iran as an alternative to direct military strikes against Tehran's nuclear programme, US intelligence sources have revealed.
"It is using hitmen, sabotage, front companies and double agents to disrupt the regime's illicit weapons project, the experts say. "The most dramatic element of the 'decapitation' programme is the planned assassination of top figures involved in Iran's atomic operations."
Iran's Press TV said: "Iran's Foreign Ministry said Tuesday that it has found traces of US and Israel's involvement in the assassination of an Iranian nuclear physics scientist."
"Primary investigations into the assassination revealed signs of the involvement of the Zionist regime [Israel], the US and their allies in Iran," ministry spokesman Ramin Mehman-Parast said.
" The Telegraph noted however that Dr Ali-Mohammadi's academic work was highly theoretical and the body responsible for the Iran's nuclear research programme said he had no connection with it.
The Financial Times said: "He was among 420 Tehran University professors who signed a petition on June 9, three days before last year's presidential election, endorsing Mir-Hossein Moussavi, the reformist candidate and now the main opposition leader. "Reformist websites hinted that this fact - rather than his possible role in the nuclear programme - might lie behind his murder.
" Kaleme, the official website of Mr Moussavi, linked the professor's death to the killing of the opposition leader's nephew, indirectly suggesting that the academic might have been killed as a way of placing more pressure on the regime's critics. " 'Following the suspicious assassination of ... the nephew of Mr Moussavi [on December 27] ... the assassination of a committed professor of Tehran University' happened, said the website.
"The bloggers were quick to suspect the murder was a plot by hardliners to scare ordinary people. Assassinations outside a victim's house, using bombs or guns, would remind many Iranians of the insecure years after the 1979 Islamic revolution."
In The Guardian, Meir Javedanfar suggested: "The probability that Mohammadi was assassinated by an Iranian opposition group such as the People's Mujahideen (MKO) may be small. However it can not be dismissed. The MKO have assassinated senior military officials in broad daylight before. A famous example was the assassination of General Ali Seyyed Shirazi, the chief of staff of the Iranian army, on his doorstep in April 1999. Although normally they would have a lot to gain by targeting a political figure, such as a senior politician, assassinating a nuclear scientist could also be beneficial to them.
Such people would be highly prized targets, and their elimination a severe embarrassment for Ahmadinejad government. It would also send a strong message to Tehran's government about the increasing intelligence-gathering capabilities of the group. It is also possible that Mohammadi was assassinated by a foreign intelligence agency.
Should that be the case, this recent incident comes amid a series of setbacks for the Oghab- 2 counter intelligence bureau. First was the mysterious death of Ardeshir Hassanpour, a nuclear scientist in January 2007. According to The Times of London, he was assassinated. This was followed by the disappearance of General Ali Reza Asgari in March 2007. Some believe that he defected to the US. And this year Shahram Amiri, a nuclear scientist, disappeared during a pilgrimage to Saudi Arabia. Some believe he defected, while other reports talk about his kidnapping. Either scenario does not bode well for Iran's intelligence community.
The Los Angeles Times said: "One student of nuclear physics told The Times she believed Ali-Mohammadi was killed because of his outspoken support for the student movement." Another said Ali-Mohammadi cut his ties with the Revolutionary Guard years ago and in recent months had been vocal in his opposition to the Islamic Republic.
"Since two months ago, he has been venting his frustration with almost everybody in the system,: said the student, who spoke on condition of anonymity. "He was openly criticizing high-ranking officials in classes."
The reformist news websites Ayandenews and Rahesabz identified Ali-Mohammadi as among a list of scholars campaigning for Mousavi during his presidential run against President Mahmoud Ahmadinejad.
Iason Athanasiadis, reporting for The Christian Science Monitor said: "One blog entry allegedly written by a former student claimed that Ali-Mohammadi had been planning on fleeing the country. The writer charged the Islamic Republic with killing him to stop his specialist knowledge from being transferred abroad.
Former students described how he advised them not to fear the regime's bullets and himself participated in the post-election opposition demonstrations. Both the government and the Green Movement denied that Ali-Mohammadi, one of Iran's first generation of nuclear physicists, was involved in his country's nuclear energy programme, pointing out that he specialised in particle physics. Where they diverged was on his loyalties, with both sides claiming him as a supporter.
Meanwhile, Al Bawaba reported: "Iranian Foreign Ministry Spokesman Ramin Mehman-Parast on Monday dismissed an Israeli newspaper report on the suspension of Iran's uranium enrichment activities as 'unfounded' and 'baseless', stressing that Tehran will continue its unabated nuclear activities.
"From our viewpoint, these newspapers and information-dissemination sources are not creditable and there is no audience for such fabrication of news and purposeful mistakes in Iran," Mehman-Parast told FNA.
Israel's Haaretz newspaper reported earlier that Iran has suspended its nuclear enrichment programme in gesture of goodwill towards the West.