At least five Iranian scientists believed to have links to the country’s nuclear programme have been attacked in the past two years, four of them fatally.

Iran maintains that its nuclear programme is for civilian purposes; western powers say Tehran is seeking to develop atomic weapons.

No group has claimed responsibility for the attacks. The Iranian authorities have accused Mossad, the Israeli intelligence agency, of being behind the assassinations and have also pointed a finger at the CIA and the UK’s MI6. In at least one case, there have been unconfirmed suspicions that the Iranian authorities themselves might have had cause to turn on the scientist killed.

Some analysts see the killings as part of broader efforts to sabotage the nuclear programme. In late 2010 Mahmoud Ahmadi-Nejad, Iran’s president, acknowledged that Iran’s push to enrich uranium had been hit by a computer virus. His comments were taken as a reference to Stuxnet, a malicious software code that has become a main tool of sabotage against Iran.

Massoud Ali Mohammadi

Killed on January 12, 2010

An expert in quantum physics at Tehran University, Ali Mohammadi was described by Iran’s government immediately following his death as a “nuclear expert”. He had served as Iran’s representative at the Sesame project, which promotes scientific co-operation among Middle Eastern counties.

However, an intelligence ministry statement described him merely as an “outstanding scientist” without mentioning his role in nuclear programmes.

He was killed when a bomb, reportedly detonated by remote control, exploded near his house. The state broadcaster said: “As a result of the bomb planted by Zionist [Israeli] and American agents, two cars and a motorcycle were severely damaged and the windows in the surrounding residential units were shattered.”

Some in Tehran suspected that, far from being an assassination by Israeli or western intelligence agencies, Ali Mohammadi’s killing might have been an act of revenge by the Iranian regime. The 50-year-old was a known sympathiser of the Green movement, which staged mass street demonstrations in Tehran following the June 2009 elections, demanding a rerun. His wife told a website linked to Iran’s domestic opposition: “Some people tell me that insiders killed my husband.”

In August 2011, the official Irna news agency reported that an Iranian, Majid Jamali-Fashi, had been sentenced to death after pleading guilty to murdering Ali Mohammadi. The prosecution said Jamali-Fashi had been acting on the instructions of Mossad. Israel, as usual, declined to comment on the claims.

Majid Shahriyari

Killed on November 29 2010

A devout Muslim fiercely loyal to Iran’s Islamic government, Shahriyari was one of the country’s leading atomic scientists. The 45-year-old worked as a physics professor Shahid Beheshti University, where he was an expert on nuclear chain reactions.

Following Massoud Ali Mohammadi’s death in January 2010, Shahriyari replaced him as Iran’s representative at the Sesame project.

He and his wife were being driven down Artesh Boulevard in northern Tehran, on their way to the university, when a motorcycle pulled alongside their car. The riders attached a device to the driver’s door window. In the moments before it exploded, Shahriyari’s wife scrambled to safety. Her husband was killed instantly.

In the wake of his death, Ali Akbar Salehi, then head of Iran’s Atomic Energy Organisation, was quoted by the official Irna news agency as saying: “Dr Shahriyari was my student for years and he had good co-operation with the Atomic Energy Organisation. One of the greatest projects of the organisation, which is a source of pride for the Iranian nation, was on his agenda.”

Fereydoon Abbasi-Davani

Wounded on November 29 2010

On the same morning on which Shahriyari was killed, Abbasi-Davani, his colleague at Shahid Beheshti University, survived a similar attack. He threw himself from his vehicle before the bomb exploded and, with his wife, was taken to hospital.

Abbasi-Davani, 52, holds a doctorate in nuclear physics and has close ties to Iran’s Revolutionary Guards. According to mashreghnews.ir, a website close to the government, he has links to elite military forces and the defence ministry.

He was reportedly one of the few experts on isotope separation at the ministry. He was listed in a 2007 United Nations resolution as a senior ministry of defence scientist involved in the nuclear and ballistic missiles programme.

Abbasi-Davani now heads Iran’s Atomic Energy Organisation. “The enemy [US and Israel] wants to frighten the nation . . .since it cannot prevent Iran’s development it attempts assassination of Iranian scientists,” he said earlier this year.

Dariush Rezaei-Nejad

Killed on July 23, 2011

A young scientist whose links, if any, to Iran’s nuclear programme are unclear, Rezaei-Nejad was shot dead in Tehran. Some reports said he was killed by two gunmen on motorcycles outside in house.

The official Irna news agency described Rezaei-Nejad as “brilliant” post-graduate student “in the field of power and electronics” at Khajeh Nasir Tusi University of Technology. It said he was the third victim of “terrorist actions … by agents of the United States and Israel” over the past two years, citing earlier killings of two nuclear scientists.

However, Iranian media subsequently backed away from statements that Rezaei-Nejad had been involved in the country’s atomic projects. The semi-official Isna news agency quoted Heidar Moslehi, Iran’s intelligence minister, as saying: “The assassinated student was not involved in nuclear projects and had no connection to the nuclear issue.”

Mostafa Ahmadi-Roshan

Killed on January 11 2011

Ahmadi-Roshan’s killing closely resembled at least two of the three previous attacks on Iranian scientists. Local media reported that the 32-year-old chemistry graduate of the capital’s Sharif University of Technology died after motorcyclists attached a magnetic bomb to his car in the centre in Tehran.

According to the semi-official Mehr news agency, he was the deputy head of Iran’s main uranium enrichment facility at Natanz.

He had been on his way to a ceremony to mark the two-year anniversary of the killing of Massoud Ali Mohammadi when the killers struck. His driver was reportedly killed by the blast and his bodyguard injured.

Shahabeddi Sadr, vice-speaker of the Iranian parliament, said the US and Israel were behind the attack. “Such blind assassinations committed during these years by American and Israeli agents did not have and will have no impact [on Iran’s development],” he said.

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