At least five people have been killed in three bomb blasts in Cairo apparently targeting police, the largest of which destroyed the facade of the police’s security directorate headquarters.

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 attacks come a day before the anniversary of the January 25 revolution in 2011 that removed Hosni Mubarak.

The blast at the directorate building shattered glass from shops hundreds of metres from the site.

"It was around seven this morning. I heard shots and then the ground shook, the windows shattered," Mohamed Taher, a shopkeeper who owns a cafe 100 metres from the blast, told Al Jazeera.

The Reuters news agency reported gunfire after the explosion. State television quoted witnesses as saying gunmen opened fire on buildings after the blast.

Smoke was seen rising over the city centre, and a large number of ambulances were seen on their way to the blast site.

Pictures on Twitter and state television showed the exteriors of buildings damaged by the blast.

The explosion destroyed a metal gate outside the multi-storey building and badly damaged its facade.

Egypt's antiquities minister, Mohammed Ibrahim, said the blast had damaged artifacts inside the museum.

No group has said it carried out the attacks. However, the Sinai-based Ansar Bait al Maqdis group issued an audio statement late on Thursday that explicitly threatened the police.