An improvised bomb has exploded at a police station in the business district of Cairo, wounding two workers, according to the state news agency.
MENA said three people on a motorcycle hurled what it called a homemade hand grenade at the police station in Giza on Monday.
There was no immediate claim of responsibility.
Egypt has been gripped by political turmoil since the army removed President Mohamed Morsi from power on July 3.
The government has killed hundreds of members of Morsi's Muslim Brotherhood, accusing them of inciting violence and committing terrorist acts.
The Brotherhood denies the allegations and accuses the army of staging a coup and trying to return Egypt to era of former President Hosni Mubarak.