A remote-controlled bomb killed a Tehran University physics professor near his home early Tuesday, in what Iranian authorities called an assassination backed by Western powers, including the U.S. and Israel.

The victim was identified as Masoud Ali Mohammadi, 50 years old. Official news reports described Mr. Mohammadi as devout, loyal to the Islamic Republic and to Supreme Leader Ayatollah Ali Khamenei. He was a member of the elite Islamic Revolutionary Guard Corps from 1980 to 2003, according to the official Iranian Fars news...