The killing of Iranian scientist Mostafa Ahmadi-Roshan is the latest in a series of mysterious incidents involving Iran’s nuclear industry and the people working in it.
Iran says its nuclear program is purely for civilian use, but Western powers believe it has military goals.
It is widely assumed that Israel and possibly the US have been actively sabotaging Iran’s nuclear program.
Here are some details of the incidents:
- Iran said deputy defence minister Ali Reza Asgari, who disappeared in Turkey in 2007, had been kidnapped by Western intelligence services. Israel and the United States denied any involvement in the disappearance.
- At the time, Turkish newspapers reported that Asgari had information on Iran’s nuclear program. Turkish, Arabic and Israeli media suggested Mr Asgari defected to the West, but his family dismissed that.
- Shahram Amiri said he was kidnapped in June 2009 when on a pilgrimage in Saudi Arabia and transferred to the United States. He said he was offered $US50 million to remain in America and “to spread lies” about Iran’s nuclear work. Three months after he disappeared, Iran disclosed the existence of a second uranium enrichment site, near the city of Qom.
- Before his disappearance, Dr Amiri worked at Iran’s Malek Ashtar University, an institution closely connected to the country’s Revolutionary Guards. Tehran initially refused to acknowledge Mr Amiri’s involvement in Iran’s nuclear program.
- Dr Amiri returned to Tehran in July 2010. Washington denied kidnapping him and insisted he had lived freely in the United States.
- Nuclear scientist Massoud Ali-Mohammadi was killed by a remote-controlled bomb in Tehran on January 12. Some opposition websites said he had backed moderate candidate Mirhossein Mousavi in the disputed 2009 election that secured president Mahmoud Ahmadinejad’s return to power.
- Iranian officials described the physics professor as a nuclear scientist but a spokesman said he did not work for the Atomic Energy Organisation. He lectured at Tehran University.
- Western sources said the professor worked closely with Mohsen Fakhrizadeh-Mahabadi and Fereydoun Abbassi-Davani, both subject to UN sanctions because of their work on suspected nuclear weapons development.
- Iran’s Bushehr nuclear power station was hit by the Stuxnet computer virus in what Tehran said was a cyber-attack by Israel and the United States. In November, Iranian president Mahmoud Ahmadinejad said that malicious software had created problems in some of Iran’s uranium enrichment centrifuges, although he said the problems had been solved.
- The New York Times said in January 2011 that the worm was the most sophisticated cyber-weapon ever deployed and appeared to have been the biggest factor in setting back Iran’s nuclear progress. Its sources said it caused the centrifuges to spin wildly out of control and that a fifth of them were wiped out.
- Two car bomb blasts killed an Iranian nuclear scientist and wounded another in Tehran on November 29, in what Iranian officials called an Israeli or US-sponsored attack on its atomic program.
- Majid Shahriyari was killed and his wife was injured. Iran’s atomic energy agency chief Ali Akbar Salehi said Dr Shahriyari had a role in one of its biggest nuclear projects, but did not elaborate, the official news agency IRNA reported. He was a lecturer at Shahid Beheshti University.
- In the other blast, Fereydoun Abbasi-Davani and his wife were both wounded. Dr Abbasi-Davani, head of physics at Imam Hossein University, has been personally subject to UN sanctions because of what Western officials said was his involvement in suspected nuclear weapons research.
- In February 2011, president Mahmoud Ahmadinejad appointed Dr Abbasi-Davani as vice-president and head of the Atomic Energy Organisation, Fars news agency reported.
- Physicist Darioush Rezai was shot dead by gunmen in eastern Tehran on July 23. The university lecturer had a PhD in physics. Deputy interior minister Safarali Baratlou said he was not linked to Iran’s nuclear program after early reports in some media said he was.
- The sound of an apparent explosion was heard from Iran’s Isfahan city on November 28, the head of the judiciary in the province said, but the province’s deputy governor denied there had been a big blast. An important Iranian nuclear facility involved in processing uranium is near Isfahan.
- The report came less than three weeks after a massive explosion at a military base near Tehran killed more than a dozen members of the Revolutionary Guard including the head of its missile forces. Iran said that explosion was caused by an accident while weapons were being moved.
- Mostafa Ahmadi-Roshan, a 32-year-old graduate of chemical engineering, was killed by a bomb placed on his car by a motorcyclist in Tehran. Another passenger died in hospital and a pedestrian was also injured.
- Iran said the victim was a nuclear scientist who supervised a department at Natanz Uranium Enrichment Facility. Iran blamed Israel and the United States for the attack.