CAIRO: A suicide car bomber struck Cairo police headquarters on Friday, the first of four blasts in Egypt's capital that killed six people on the eve of the anniversary of the 2011 uprising.

The bombings, all targeting the police, came as street clashes between Islamist supporters of deposed president Mohamed Morsi and backers of the military killed eight people, a day before planned rallies to mark the revolt that drove Hosni Mubarak from power.

In the first attack, an assailant rammed a bomb-laden car into a metal fence surrounding the Cairo security directorate before dawn, killing four people and wounding more than 70, police and the health ministry said.

The blast, which badly damaged the facade of the building, left a large crater in the ground and sent a plume of smoke billowing over the city.

Policeman Mahmud Mushref, his head bandaged after being wounded in the blast, said the car had slammed into the fence surrounding the building.

“I was on the third floor, with the head of security,” said Mushref. “The car crashed into the fence, and the explosion happened.” Interior ministry spokesman Hany Abdel Latif said “the vehicle tried to get close to the building but was stopped at the gate. Casualties were relatively small given the size of the blast.”

The bombing also damaged the nearby Museum of Islamic Art, bringing down ceilings and damaging exhibits, culture minister Mohamed Ibrahim said.

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

Hours later, a small makeshift bomb exploded near a police vehicle close to a metro station in the neighbourhood of Dokki, killing a police conscript, security officials said.

Two other bombs went off hours apart in a neighbourhood close to the Giza pyramids, one killing a person and wounding four conscripts near a cinema.

The other struck outside a police station, without causing any casualties, police said.

“They don't want the people to celebrate” the Jan 25 anniversary, the interior minister, said of the assailants.

The president's office vowed to “avenge our martyrs”.

“Whoever planned, participated, financed, or incited (the attack) will be punished with the worst form of punishment,” it said.

Later, at least eight people were killed when Islamist protesters clashed with their civilian opponents and police in several cities, said security officials and state media.

Deadly clashes between supporters and opponents of Morsi have become a weekly ritual since the former president's overthrow.

The pro-Morsi National Pro-Legitimacy Alliance condemned the bombing of the security headquarters but said it would go ahead with its “peaceful struggle against (the) coup”.

The deadliest bombings since Morsi's overthrow have been claimed by Ansar Beit al-Maqdis, Al Qaeda-inspired group led by Bedouin militants in the Sinai Peninsula.

“The first bombing... has Ansar Beit al-Maqdis's name all over it,” said David Barnett, a researcher on militant groups in Egypt with the Foundation for the Defence of Democracies think-tank.

“The latter three might be different actors trying to take advantage of the situation,” said Barnett, referring to the apparently amateurish devices used in the attacks.

My building shook: A witness who lives in an apartment about 200 metres (yards) away from the police headquarters said he had been awakened by the explosion.

“My building shook,” Yahya Attiya said.

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

The Brotherhood had also denied involvement in previous bombings, 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.

Ansar Beit al-Maqdis claimed responsibility for that attack, but many blame the Brotherhood.—AFP