A blast near a police headquarters in central Cairo has claimed at least four lives and injured dozens. Witnesses say gunfire was also heard.
According to security sources, the explosion was probably caused by a car bomb. The dead included three policemen.
The blast damaged a building and sent smoke rising above the city centre. State television said gunmen opened fire on buildings after the explosion.
Hours after the attack, two more blasts rocked the capital.
A crude explosive device killed one policeman and wounded nine others in another Cairo neighborhood whereas a third explosion went off near a police station in Giza, a large district on the outskirts of Cairo. There were no immediate reports of casualties.
There was no immediate claim of responsibility for the attack.
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It comes before the third anniversary of the uprising that ousted Hosni Mubarak.
Prime Minister Hazem el-Beblawi condemned the Cairo Security Directorate attack in a statement, saying it was an attempt by "terrorist forces" to derail the political road map which was, nevertheless, being implemented "firmly".
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.