Iranian state radio says a prosecutor was shot to death by a gunman in the central city of Isfahan.
The report said the provincial deputy prosecutor, Ahmad Reza Tavallai, died after a gunman shot him at close range in front of his office early Monday.
According to the report, the assailant, a 50-year-old man, then surrendered to police.
Murdering judges is often seen as part of a personal vendetta by convicts or their relatives.
More than 150 convicts were hanged in Iran in 2008 for crimes such as armed robbery, rape, drug trafficking and murder.
Earlier in January, a senior judge was shot dead in the southeastern province of Khuzestan. In 2005 another prominent judge was killed in Tehran.