Three bombs hours apart hit Cairo police headquarters and policemen in the Egyptian capital, killing at least four people on the eve of the anniversary of the 2011 uprising against Hosni Mubarak.

The first bomb struck the Cairo security directorate around 6.15am on Friday (1515 AEDT), killing four people and wounding more than 70, the health ministry said.

Hours later, another bomb, a small makeshift device, was set off near a metro station, followed by a bomb outside a police station on a road leading to the Giza pyramids.

The attacks came a day before police were to deploy across the capital for the third anniversary of the uprising against Mubarak, with Islamists calling for mass protests against the new regime.

A witness to the police headquarters bombing said a booby trapped car had stopped at the metal fence surrounding the building before the bomb went off.

“I was on the third floor, with the head of security,” said the policeman, Mahmud Mushref, his head bandaged after he was injured in the blast.

“The car crashed into the fence, and the explosion happened.”

The explosion left a large crater in the ground and sent a plume of smoke billowing above the city.

The health ministry said at least four people were killed and 76 wounded.

“Casualties were relatively small given the size of the blast,” said interior ministry spokesman Hany Abdel Latif.

A witness who lives in an apartment about 200 metres from the police building said he had been woken up by the explosion.

“My building shook,” Yahya Attiya said.

Hours later, the small bomb set off near a central Cairo metro station wounded five policemen, the health ministry said.

State television reported one person was killed in the blast, but it was not immediately possible to confirm the fatality.

The facade of police headquarters and the front of the nearby Museum of Islamic Art were badly damaged by the earlier blast.

The interior ministry said the bomb was detonated by the high metal fence surrounding the police building.

Riot police pushed back hundreds of onlookers, some of whom chanted slogans against the Muslim Brotherhood.

Militants have escalated attacks since the military overthrew Islamist president Mohamed Morsi in July.

Morsi’s Muslim Brotherhood has denied involvement in the attacks, but was blacklisted as a terrorist group after 15 people were killed when a suicide bomber blew up a vehicle at a police headquarters north of Cairo in December.

An al-Qaeda inspired group, Ansar Beit al-Maqdis, claimed responsibility for that attack.

The Brotherhood has called for protests starting on Friday to mark the January 25 anniversary of the 2011 uprising against Mubarak, accusing the military-backed government of continuing autocratic rule.

The country has been deeply divided since Morsi’s overthrow, between his Islamist supporters and backers of the military which accuses the Brotherhood of terrorism.

The Brotherhood has condemned previous attacks against the police and army since Morsi’s overthrow.

Scores of soldiers and police have been killed in the restive Sinai Peninsula and militants in the desert region have begun to expand their operations to densely populated areas of the rest of the country.