At least five people have been killed in three bomb blasts in Cairo apparently targeting police. The first blast at the police HQ, at about 6:15am local time, killed four and injured about 70 others, according to state sources. The blast, reportedly a bomb in a vechicle, also damaged the nearby Museum of Islamic Art building. In a second blast hours later, a small IED was detonated next to police vehicles near the Behooth metro station in the Dokki district. One person was reported killed in the explosion. A third blast hit a police directorate in Talbiya, in Giza. The explosion was caused by a crude home-made device, police said, and there were no casualties. The explosions came one day before the third anniversary of the revolution that brought down Hosni Mubarak, Egypt's third and longest-serving president. Al Jazeera's Mike Hanna reports from Doha.