The US has dismissed allegations by Iran that American and Israeli agents were responsible for the killing of a physics professor in Tehran.
The US State Department described the accusation as "absurd".
Physicist Massoud Ali Mohammadi died in a bomb blast on Tuesday, Iranian media reported, describing him as a nuclear scientist and a government supporter.
But later reports suggested he was not involved in Iran's nuclear programme and had signed an opposition petition.
Mr Ali Mohammadi, 50, was killed by a remote-controlled bomb near his home.
Full story by BBC News at 22:15 GMT, Tuesday, 12 January 2010:
US denies killing Iran scientist Massoud Ali Mohammadi
