A prominent supporter of Iran's leading opposition politician was killed by a bomb at his home yesterday.

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 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.