An Iranian university professor working at a key nuclear facility has been killed in a bomb explosion, the latest in a series of assassinations and attempted killings linked by the country's authorities to a secret war by Israel and the US to stop the development of what Tehran insists would be a peaceful nuclear capability.

Mostafa Ahmadi Roshan, 32, a chemistry expert and a director of the Natanz uranium enrichment plant in central Iran, died after two assailants on a motorcycle attached magnetic bombs to his car, according to the semi-official Fars news agency.

Two other Iranian nationals were reported injured in the blast, which comes at a time of rising international tension.

Safar Ali Baratloo, a senior security official, was quoted by Fars as saying the attack was the work of Israelis.

"The magnetic bomb is of the same types already used to assassinate our scientists," he said. "The terrorist attack is a conspiracy to undermine the [2 March] parliamentary elections."

Israeli officials have previously hinted about covert campaigns against Iran without directly admitting involvement.

On Tuesday, Israeli military chief Lieutenant General Benny Gantz was quoted as telling a parliamentary panel that 2012 would be a "critical year" for Iran in part because of "things that happen to it unnaturally".

The incident resembles earlier attacks on scientists allegedly connected to Iran's nuclear programme. Tehran University physics professor Masoud Ali Mohammadi was killed on 12 January 2010, when a remote-controlled bomb attached to a motorcycle exploded near his car as he was preparing to leave for work.

In November 2010, a pair of back-to-back bomb attacks in different parts of the capital killed one nuclear scientist and wounded another. Majid Shahriari, the scientist who died, was a member of the nuclear engineering faculty at Shahid Beheshti University in Tehran and co-operated with the Atomic Energy Organisation of Iran. The wounded scientist, Fereidoun Abbasi, was almost immediately appointed head of Iran's atomic agency.

And in July 2011, motorcycle-riding gunmen killed Darioush Rezaeinejad, whom initial Iranian reports described as a scientist involved in the country's nuclear programme. Officials later denied Rezaeinejad had any links to the programme, but blamed his killing on the US and Israel.

The latest blast is certain to bring fresh charges by Iran that the US and its allies are waging a clandestine campaign of bloodshed and sabotage in attempts to set back Iran's nuclear efforts.

"Instead of actually fighting a conventional war, western powers and their allies appear to be relying on covert war tactics to try to delay and degrade Iran's nuclear advancement," Theodore Karasik, a security expert at the Dubai-based Institute for Near East and Gulf Military Analysis told Associated Press.

He said the use of magnetic bombs bore the hallmarks of covert operations.

"It's a very common way to eliminate someone," he added. "It's clean, easy and efficient."

The US and other countries claim Iran is trying to develop nuclear weapons technology. Iran denies the allegations, saying its programme is intended for peaceful purposes.