Israel's Mossad is behind the assassination of an Iranian nuclear scientist last week, the German weekly Der Spiegel reported, quoting "a source in Israel's intelligence community."

Last week, Dariush Rezaeinejad, a 35-year-old member of the Atomic Energy Organization of Iran, was shot dead by two gunmen firing from motorcycles. This is the fourth attack on an Iranian nuclear scientist in the past year. In the previous cases, Iranian media outlets and spokesmen accused the Mossad, the CIA and MI6 of being behind the strikes.

Open gallery view Technicians measuring parts of Iran's Bushehr nuclear power plant in this undated photo. Credit: AP

"This was the first public operation of the new Mossad chief Tamir Pardo," an Israeli intelligence official reportedly told Der Spiegel.

The report also claimed that there is a fierce debate in Israel over the efficiency of such assassinations and it also stated that Israel Air Force officers have stepped up their calls to bomb Iran's nuclear reactor.

"Mossad experts have long believed that the best way to delay the progress of Iran's nuclear program is by assassinating key targets involved in its development and by striking Iran's nuclear reactors – but it is unclear when Prime Minister Benjamin Netanyahu will listen to these suggestions," the article said.

The man, who was killed last Saturday, was initially identified by state-run media as Darioush Rezaei, a physics professor and expert in neutron transport. The media then backtracked, with officials subsequently naming him as Dariush Rezaeinejad, an electronics PhD student.

Foreign officials contacted by the Associated Press have verified the name, but say that Rezaeinedjad participated in developing high-voltage switches, a key component that is crucial to setting off the explosions needed to trigger a nuclear warhead.