Judges and other officials have been previously targeted by militants who are opposed to President Abdel Fattah al-Sisi and who are angered by the prison sentences handed down to members of the Muslim Brotherhood.
The Muslim Brotherhood was previously the largest party in the parliament – it is now banned and former president, Mohammed Morsi, has been sentenced to death for his role in a mass jailbreak.
Hisham Barakat’s place of work was targeted earlier this year when a bomb exploded near the high court in central Cairo, killing two people.
Video recorded a short time after the explosion shows a black plume of smoke rising into the air and several burned-out cars. The glass in the windows of nearby buildings was also shattered.