Mohsen Fakhrizadeh, who was assassinated in Tehran on Friday, is the latest Iranian nuclear scientist to be attacked since 2012.
Fakhrizadeh died of injuries in hospital after assassins fired on his car, Iran's armed forces said in a statement carried by state media. He had been described by Western, Israeli and Iranian exile opponents of Iran's clerical rulers as a leader of a covert atomic bomb programme halted in 2003.
Iran has long denied seeking to weaponise nuclear energy.
Here are some details of other attacks on Iranian scientists in recent years:
Nuclear scientist Massoud Ali-Mohammadi was killed by a remote-controlled bomb in Tehran on Jan. 12, 2010. Some opposition websites said he had backed moderate candidate Mirhossein Mousavi in the disputed 2009 election that secured a second presidential term for Mahmoud Ahmadinejad.
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 Fakhrizadeh and Fereydoun Abbassi-Davani, who were both subject to U.N. sanctions because of their work on suspected nuclear weapons development.
A list of Ali-Mohammadi's publications on Tehran University's website suggested his specialism was theoretical particle physics, not nuclear energy, a Western physics professor said.
Shahriyari was killed and his wife was wounded in a car bomb blast in Tehran on Nov. 29, 2010, in what Iranian officials called an Israeli or U.S.-sponsored attack on its atomic programme.
Iran's atomic energy agency chief Ali Akbar Salehi said 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.
Abbasi-Davani and his wife were hurt in a car bomb blast on the same day as Shahriyari was killed.
Abbasi-Davani, who was head of physics at Imam Hossein University, had been personally subject to U.N. sanctions because of what Western officials said was his involvement in suspected nuclear weapons research.
The intelligence minister at the time, Heydar Moslehi, later said: "This terrorist act was carried out by intelligence services such as the CIA, Mossad and the MI6. A group that wanted to carry out a terrorist act but did not succeed, was also arrested. They confessed that they were trained by these intelligence services."
Abbasi-Davani was appointed vice-president and head of the Atomic Energy Organisation in February 2011, Fars news agency reported, but was removed in August 2013, the state news agency IRNA reported.
Rezai, 35, was shot dead by gunmen in eastern Tehran on July 23, 2011. 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.
Ahmadi-Roshan, a 32-year-old chemical engineering graduate, was killed by a bomb placed on his car by a motorcyclist in Tehran in January 2012. Another passenger died in hospital and a pedestrian was also injured. The attack was similar to that in November 2010.
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.