An improvised bomb exploded at a police station in downtown Cairo on Monday, wounding two workers, the state news agency said.
MENA said three people on a motorcycle hurled what it called a homemade hand grenade at the police station. There was no immediate claim of responsibility.
Egypt has been gripped by political turmoil since the army ousted Islamist President Mohamed Mursi on July 3.
The military-backed government has killed hundreds of members of his Muslim Brotherhood, which they accuse 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 the repressive era of former president Hosni Mubarak.
Egypt faced an Islamist insurgency in the 1990s, when bombing and shooting attacks destabilized the country and hurt tourism.
Improvised bomb wounds two at Cairo police station