Iran isn’t the most transparent of countries, so it’s hard to know whether this is  another country’s attempt to slow down the Iranian nuclear program, something to do with Iranian politics or something else entirely.

What follows is excerpted from BBC correspondent  Mohsen Asgari’s report Iran car explosion ‘kills nuclear scientist’ in Tehran

A university lecturer and nuclear scientist has been killed in a car explosion in north Tehran, reports say. Mostafa Ahmadi-Roshan, an academic who also worked at the Natanz uranium enrichment facility, and another unidentified person were killed in the attack. The blast happened after a motorcyclist stuck an apparent bomb to the car. Several Iranian nuclear scientists have been assassinated in recent years, with Iran blaming Israel and the US.

Both countries deny the accusations. Iran’s Vice-President Mohammad Reza Rahimi told state television that the attack against Mr Ahmadi-Roshan would not stop “progress” in the country’s nuclear programme. He called the killing “evidence of [foreign] government-sponsored terrorism”. Local sources said Wednesday’s blast took place at a faculty of Iran’s Allameh Tabatai university. Two others were reportedly also injured in the blast, which took place near Gol Nabi Street, in the north of the capital. ‘Magnetic bomb’

Mr Ahmadi-Roshan, 32, was a graduate of Sharif University and supervised a department at Natanz uranium enrichment facility in Isfahan province, semi-official news agency Fars reported. “The bomb was a magnetic one and the same as the ones previously used for the assassination of the scientists, and the work of the Zionists [Israelis],” deputy Tehran governor Safarali Baratloo said.

Witnesses said they had seen two people on the motorbike fix the bomb to the car, reported to be a Peugeot 405. A second person died in the attack though the car itself remained virtually intact. The BBC’s Mohsen Asgari, in Tehran, says that the explosion was caused by a targeted, focussed device intended to to kill one or two people and small enough not to be heard from far away.