The first explosion hit police headquarters in Cairo before Friday prayers. <br /><br />The nearby Islamic Art Museum was badly damaged.<br /><br />There was a second explosion a few hours later near a metro station in the Dokki district of Giza. <br /><br />Then a third blast near a police station in Al-Ahram area of Giza.<br /><br />The fourth explosion also in Giza - in front of a cinema.<br /><br />Al Jazeera's Richard Martin reports.
