The Muslim Brotherhood organization in underground acts of terror began again, Third blast in Cairo 5 people kill.

The bombings came on the eve of the anniversary of the start of the 2011 uprising that toppled Egypt’s ruler Hosni Mubarak.

Three blasts hit Cairo on Friday, targeting police HQ, a metro station and a police station. They apparent string of militant attacks claimed at least five people and injured scores of others.

The latest explosion was reported near a police station in the suburbs of the Egyptian capital. The explosion, in the west Cairo Talebiya district on the main road leading to the Giza pyramids, caused no fatalities.

Minutes earlier a blast killed at least one person and injured 15 near the Behooth subway station. State TV reported that it was caused by a crude explosive device.

But a conflicting report said the blast happened in a drive-by attack on security vehicles, in which the attacker threw a hand grenade.

The early morning blast on the police headquarters in Cairo was the highest profile attack on security forces in months. It was carried out by a suicide bomber in an explosive-laden car, which detonated in front of the building.

The Friday morning explosion at the Cairo Security Directorate left four people dead and injured 73 others, according to the Health Ministry.

Pictures from the scene show damaged fronts of several buildings in Port Said street, including the police headquarters and the famous Museum of Islamic Art..

Witnesses reported injured people being dragged out of the damaged building and transferred into ambulances.

The body of the suspected suicide bomber, who apparently drove the car to the building, was found.

The blast was powerful enough to be heard from kilometers away in all directions. It also sent a large plume of black smoke into the sky.

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

There were also reports of machine gun fire in the area following the explosion, indicating a likely militant attack. Witnesses said they saw gunmen on motorbikes shooting at the police HQ just after the bomb went off.

Egyptian state TV showed a crowd standing in front of the HQ building in the wake of the blast, chanting “people demand the execution of the Muslim Brotherhood.”

Egyptian security troops and army soldiers have been facing regular militant attacks since July 2013, when a military coup deposed Islamist President Mohamed Morsi.

There have been at least three bomb attacks in the last weeks in the country, including a suicide coming at a police compound in Mansoura, north of Cairo, which killed 15 people.

“We don’t know who is behind these bombings, but it seems likely that they are part of a pattern of bombings carried out by jihadist militants with links to the war, which is raging in the Sinai. And the message to the Egyptian government is: ‘We do not accept your constitution, we do not accept your government, we see them as traitors and we want to bring the whole house crashing down,’” Cairo-based journalist Hugh Miles told RT.

The attack on police HQ on Friday and the second blast come less than a week after Egyptians approved a new constitution, despite a vote boycott by Morsi’s Muslim Brotherhood, which was outlawed after the coup.

The Brotherhood was planning a massive protest after Friday prayers across the country, the largest in a series of similar events.

The bombings raise new concerns over security during the upcoming anniversary celebrations of the 2011 revolution, which ousted Egypt’s long-time ruler Hosni Mubarak. The Interior Ministry pledged to protect the Saturday celebration.

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