Officials said the bombs apparently were targeting Central Security Forces trucks deployed on the Giza Bridge, Ahram Online reported.
Security forces had been deployed in advance of expected protests by supporters of ousted President Mohamed Morsi in several locations in Cairo and Giza.
Ahram Online also reported a police officer's private vehicle was set on fire Friday in the city of 6 October near Cairo.
Morsi was ousted July 3 amid protests against his regime. His supporters have been protesting regularly, demanding he be reinstated.