Five people have been killed, the majority of them police officers, and about 90 wounded after three blasts in the Egyptian capital that appeared to target the police force.

The main car bomb attack caused extensive damage to the Cairo Security Directorate, the building which is home to both the police and state security and as such is one of the most heavily-guarded in the country.

Witnesses told state TV reporters that gunmen on motorcycles also opened fire on the building in the wake of the explosion at around 6.30am local time, while Reuters quoted sources saying three of those killed were members of the police.

Just hours later a second bomb attack targeted security vehicles at a metro station in the capital.

Egyptian state TV said one person was killed and 15 were injured when a person driving past the station threw a hand grenade in the direction of the police.

Shortly afterwards a third blast, also reportedly caused by a hand grenade, targeted a small police station in the Cairo suburbs around two miles from the famous Giza Pyramids. No one was killed.

The attacks come on the eve of the third anniversary of the 2011 uprising.

The revolution forced the country’s decades-long ruler Hosni Mubarak to resign.

An al-Qaeda-inspired militant group Ansar Beit al-Maqdis (Champions of Jerusalem) has said it carried out the attack on the police headquarters.

The group previously claimed responsibility for a car bomb attack on a security building in the northern city of Mansoura in December that killed 16 people and injured more than 100 others.

The authorities blamed the Muslim Brotherhood for that attack – something the group strongly denied – and declared it a terrorist group shortly afterwards.

An angry group gathered outside the bombed police headquarters, accusing the Islamist movement of being behind today’s attacks, some shouting: “Death to the Muslim Brotherhood.”

The Muslim Brotherhood, however, denied complicity in what it called the “cowardly bombings.

Egypt’s Interior Minister Mohammed Ibrahim described it as a “vile terrorist act.”

Egypt has been plunged into bouts of violence since the July military coup against Morsi and following heavy-handed security crackdown left hundreds of Muslim Brotherhood supporters dead and thousands arrested.

While car bombings are more common in remote, conflict-ridden regions of Egypt like the Sinai Peninsula, they remain rare occurrences in the capital itself.