(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.
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A huge explosion strikes Cairo's police headquarters, damaging several floors
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More than 50 people also are wounded in the attack, state media report
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Smaller blasts follow in other areas of Cairo, wounding several people
Friday is a holiday in @placeholder, so the police headquarters is unlikely to have been as busy as it would have been on a weekday.