Train passengers were trapped underground and TV stations knocked off air in an incident opponents say demonstrates the government's inability to keep the lights on.
Abdul-Fattah el-Sisi has promised to wipe out the Muslim Brotherhood if elected later in May. This may cause more, not less, instability.
The mass trial of alleged Muslim Brotherhood members opened and closed in Minya on Tuesday. Sentencing will take place on April 28.
An Egyptian court sentenced 529 members of the Muslim Brotherhood to death for the murder of a police officer during unrest last year.