People inspect a destroyed taxi cab at the site of the explosion.
Security cam catches explosion in Cairo
02:56 - Source: CNN

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NEW: Official: U.S. is "aware of reports" one of its citizens has been detained in Egypt

A huge explosion strikes Cairo's police headquarters, damaging several floors

More than 50 people also are wounded in the attack, state media report

Smaller blasts follow in other areas of Cairo, wounding several people

CNN  — 

A plume of black smoke rose over Cairo early Friday after a powerful explosion hit the city’s police headquarters, killing at least four people and wounding more than 50 others, Egyptian authorities said.

The blast struck a key symbol of authority in a country that has been shaken by political turmoil and violent unrest in recent years.

It was followed by two smaller explosions near police stations in the Cairo area, one of which killed one person.

And later, a fourth explosion outside a movie theater in Giza city, near Cairo, killed one person and injured seven others, state television said.

The blasts took place at a time of high tension – the day before the third anniversary of the 2011 revolution that eventually brought down authoritarian leader Hosni Mubarak.

And they come amid the instability ushered in by the military’s overthrow last year of the democratically elected former President, Mohamed Morsy, and the ensuing crackdown by security forces on the Islamist movement that supported him, the Muslim Brotherhood.

Suicide bomber suspected

The first blast appeared to have been caused by a suicide attacker who tried to drive a vehicle laden with explosives into the police headquarters, said Maj. Gen. Hany Abdel Latif, a spokesman for the Interior Ministry, citing preliminary reports.

Guards stationed in front of the headquarters in the Abdeen district of Cairo opened fire at the vehicle, and the explosion went off in the building’s vicinity rather than inside, he told state news agency Egynews.

The blast destroyed the front of the first and second floors of the eight-story building, he said, and damaged the third floor.

Most of the building’s windows appeared to have been blown out. Air-conditioning units dangled by cables from the shattered facade.

At least 51 people were wounded in the explosion, state-run broadcaster Masriya TV reported, citing the Health Ministry.

Visiting the ruined building, Egyptian Interior Minister Mohamed Ibrahim condemned the bombing.

“These are nothing but desperate attacks in an attempt to create chaos, but the citizens here will remain resilient,” he told Masriya TV.

Ibrahim said security forces will ensure that Egyptians will be able to celebrate the anniversary of the revolution Saturday “as if nothing happened today.”

A powerful blast

CNN’s Reza Sayah said the blast appeared to be “the most powerful bomb attack that we’ve seen here in central Cairo in recent memory.”

Speaking from near the scene of the blast, he said the attack will probably intensify the fight between Egypt’s military-backed government and the groups that oppose it.

It wasn’t immediately clear who was behind that bombing.

Friday is a holiday in Egypt, so the police headquarters is unlikely to have been as busy as it would have been on a weekday. The blast happened around 6:30 a.m., according to state media.

Hundreds of people – some stunned, some angry – gathered around the scene, Sayah said. Many of those in the crowd were quick to blame the Muslim Brotherhood, despite no official word on who might be to blame.

The Muslim Brotherhood denied responsibility for the bombing and issued a statement condemning it.

“The Muslim Brotherhood condemns any acts of violence or killing, regardless of who are the perpetrators, and the (Muslim Brotherhood) emphasizes that the revolution that has continued for seven months is a peaceful revolution and it will insist to remain peaceful.”

Separately, the Muslim Brotherhood called for protests and sit-ins across multiple sites in and out of Cairo in a show of defiance. The group said security forces fired live ammunition on demonstrators in Beni Suef on Friday; surrounded and mistreated worshippers at a mosque in S