An Egyptian policeman has been injured after an explosive device went off on Thursday, Al Ahram's Arabic news website reported.
The officer was wounded as he dealt with the bomb found in a central area near the defence ministry and Ain Shams University.
Explosives experts were sent to search the area.
Egypt has been subject to a rising wave of militant attacks since the ouster of former Islamist president Mohamed Morsi last year. The repeated assaults have claimed the lives of hundreds of security forces and at times injured civilians.