Bombs rock Cairo on uprising anniversary

A suicide bomber struck Cairo police headquarters in the first of three bombings in the Egyptian capital that killed five people ahead of the anniversary of the 2011 uprising.

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

In the first attack, an assailant rammed a bomb-laden car into a metal fence surrounding the Cairo security directorate at around 6.15am (3.15pm AEDT, killing four people and wounding more than 70, police officials and the health ministry said.

The bombing damaged the nearby Museum of Islamic Art, bringing down ceilings and damaging a relic wooden prayer niche from the medieval Fatimid period, culture minister Mohamed Ibrahim told AFP.

Hours later, another bomb, a small makeshift device, was set off near a police vehicle close to a metro station, killing a police conscript, security officials said.

That was followed by a third outside a police station on a road leading to the Giza pyramids. It caused no casualties, the interior ministry said.

Friday is the Muslim day of prayer and rest and so relatively few people were on the streets.

State television said investigators had found the remains of the suspected suicide bomber.

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

"My building shook," Yahya Attiya said.

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

Militants have escalated attacks since the military overthrew Morsi after only a year of turbulent rule.

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, but many blame the Brotherhood.