Bomb kills Iranian nuclear expert

The government immediately blamed the death of nuclear physics professor Masoud Ali Mohammadi on a rebel group it claimed was backed by the US and Israel.

But critics were quick to point out that Mr Mohammadi's death followed a call by hard-line government supporters for the execution of opposition leaders.

Mr Mohammadi, 50, was a professor at Tehran University, which has been at the centre of recent protests by student opposition supporters.

Before the election, pro-reform websites published his name among a list of 240 Tehran University teachers who supported the government's main opponent Mir Hossein Mousavi.

The US dismissed any suggestion of its involvement as "absurd". Israel's Foreign Ministry would not comment.

Another Iranian nuclear scientist, Shahram Amiri, disappeared in June while on a pilgrimage to Saudi Arabia, raising questions about whether he defected and gave the West information on the country's nuclear programme.

Mr Amiri worked at a university linked to the Revolutionary Guard and his wife said he was researching medical uses of nuclear technology at a university.

Iran's foreign minister accused the US of helping to kidnap him and demanded his return.

Mr Mohammadi had just left his house on his way to work when the remote-controlled explosion went off in northern Tehran's Qeytariyeh district.

Mr Mohammadi wrote several articles on quantum and theoretical physics in scientific journals.

He was not known as an outspoken or visible supporter of Iran's opposition movement in the post-election turmoil, although his name did appear on the list of professors who backed Mr Mousavi before the vote.

Mr Mousavi and his supporters claim he won the June election but fraud robbed him of his victory. His supporters staged massive street protests in the weeks after the election, which met with a harsh government crackdown.

Iran's Foreign Ministry accused Israel and the US of involvement in the assassination.

"In initial investigations, there are some indications of vices of the Zionist regime, the US and their mercenaries in Iran in the terrorist incident," a ministry spokesman said.

The West has been pushing Iran to halt its uranium enrichment programme, a technology that can be used to make fuel for power plants but which also offers a possible pathway to weapons development.

Israel has threatened to take military action if diplomatic efforts fail.

US Secretary of State Hillary Clinton said yesterday that the Obama administration has concluded that the best way to pressure Iran to come clean on its nuclear ambitions is to impose sanctions aimed at the country's ruling elite.

Iran is already under three sets of UN sanctions for refusing to freeze its enrichment work.