One senior physicist killed and another wounded in coordinated attacks in Tehran, raising the question of whether there is a nuclear hit-team at work

Assassins on motorbikes have killed an Iranian nuclear scientist and wounded another in identical attacks this morning. They drove up to the scientists' cars as they were leaving for work and attached a bomb to each vehicle which detonated seconds later.

The man who was killed was Majid Shahriari, a member of the engineering faculty at the Shahid Beheshti in Tehran. His wife was wounded. The second attack wounded Fereidoun Abbasi, who is also a professor at Shahid Besheshti University, and his wife.

They are senior figures in Iranian nuclear science. Abbasi was a member of the Islamic Revolutionary Guards, or Pasdaran, and once taught at the Pasdaran-run Imam Hossein University. He was hailed by Mahmoud Ahmadinejad three years ago as Iran's academic of the year.

Abbasi is named on UN Security Council resolution 1747 as being "involved in nuclear or ballistic missile activities". The resolution describes him as a "Senior ministry of defence and armed forces logistics scientist with links to the Institute of Applied Physics, working closing closely with Mohsen Fakhrizadeh-Mahabadi" - believed by Western intelligence to be (or have been) in charge of the Iranian nuclear weapons programme.

Shahriari co-authored a paper on neutron diffusion in a reactor core with Ali Akbar Salehi, the head of the Iranian Atomic Energy Organisation. Salehi said today Shahriari was in charge of a major project at AEOI.

The attacks bear some similarities to the assassination of another nuclear physicist, Masoud Ali Mohammadi, in January. In that attack, the bomb was strapped to a motorcyle and detonated by remote control.

You do not have to look far to see a pattern. All three had professional links. Shahriari and Ali Mohammadi were both member of the Sesame Council, which runs a particle accelerator called a synchrotron in Jordan, which brings together scientists from across the region, including Israel. Ali Mohammadi and Abbasi both taught at the IRGC's Imam Hussein University, while both Shahriari and Abbasi are listed as members of the Nuclear Society of Iran.

If the Security Council is right, Abbasi was clearly deeply involved in banned activities. The picture is not as clear with the other two victims. Ali Mohammadi's friends and colleagues insisted he had nothing to do with the banned programme, but Rahesabz, an online news site with links to the Green movement, said he was "involved in Iranian defence programmes, including nuclear facility programmes and was in possession of classified information."

President Mahmoud Ahmadinejad was quick to assign blame. He was quoted by IRNA, the state news agency as saying: "Western governments and the Zionist regime were involved in today's assassinations in Iran."

It does seem that someone is working their way down a hit-list, perhaps striking as and when targets become vulnerable. The culprits could be anyone with the objective of degrading Iran's nuclear capacity. From a completely callous point of view, it does not matter if the targets are central figures. University teachers are turning out the next generation of Iranian nuclear scientists, and a source of expertise on which the state nuclear programme can draw at any time.

One local suspect would be the Sunni Jundullah movement, which today put up a video of a captive called Amir Hossein Shirani, described as a worker in Iran's secret nuclear complex, confessing to the existence of a weapons programme.

However, the video makes no claim of responsibility for the two attacks today, which would in any case represent something of a leap in sophistication for Jundullah operations. There are also reasons to be sceptical of the role of the People's Mujahedin (MeK or PMOI), which has not participated in any such attacks for years and is currently attempting to clean up its image to get off the state department's terrorist organisations list.

One possibility is that this is a smaller, more tightly-knit group, trained and funded abroad with the specific task of picking off members of Iran's nuclear elite. We know that both the US and Israel have active and wide-ranging programmes aimed at sabotaging the Iranian nuclear programme, which has clearly been experiencing severe problems in recent months.

Ahmadinejad today provided the first high-level admission that the Stuxnet computer worm, unleashed earlier this year and widely attributed to the Israelis, had caused problems for Iran's centrifuge programme. According to Reuters, he told a news conference:

They succeeded in creating problems for a limited number of our centrifuges with the software they had installed in electronic parts. They did a bad thing. Fortunately our experts discovered that and today they are not able [to do that] anymore.



The last possibility is that these scientists have been killed by the state either for giving away secrets, or on suspicion of contemplating defection. The fact that that two of the victims were members of the Sesame Council, with contact with Israelis and westerners, could be seen as possible pointers in that direction.

But the costs to Iran of killing its own would be high indeed. The state would lose valuable human capital, knowedgeable scientists teaching the next generation of nuclear specialists, and the assassinations would put any young Iranian off a career in nuclear science. On balance, it seems more likely that this killings have been carried out by enemies of the Islamic Republic rather than its friends.