Twenty-four year old Majid Jamali Fashi was hanged at Tehran's Evin Prison after being sentenced to death in August last year for the murder of Massoud Ali-Mohammadi, Iran's state news agency quoted the central prosecutor's office as saying. It said he had confessed to the crime.

Ali-Mohammadi was killed in January 2010 when a remote-controlled bomb attached to a motorcycle outside his home in Tehran went off.

Tuesday's report said Fashi had travelled abroad on several occasions to receive training from Mossad before returning to Iran to plot the assassination.

Yet Western analysts said Ali-Mohammadi, a 50-year-old Tehran University professor, had little, if any, role in Iran's sensitive nuclear programme. A spokesman for Iran's Atomic Energy Organisation said at the time he was not involved in its activities. The most recent attack on an Iranian scientist occurred in January. Mostafa Ahmadi-Roshan - a deputy director of the Natanz uranium enrichment facility - was killed when a magnetic bomb planted on his vehicle detonated.

Tehran has accused Israel and the United States of assassinating four Iranian scientists in order to sabotage its controversial nuclear programme. Washington has denied any U.S. role, while Israel has declined to comment.

Last month, Iranian intelligence officials said they had arrested 15 people they called a "major terror and sabotage network with links to the Zionist regime". The group had plotted to assassinate an Iranian scientist in February, the authorities said.

Iran denies Western accusations it is seeking to develop a nuclear weapons capability, but major powers are pushing Tehran to become more transparent and cooperative ahead of talks later this month.

British Foreign Secretary William Hague on Monday warned the European Union would impose tougher sanctions on Iran if it failed to take concrete steps to allay international concerns over its nuclear programme. AFP