Egypt's state-run news agency MENA said the blast occurred near a mosque on Pyramids road which leads from city centre to the Giza pyramids.
Six policemen, including two officers, were killed, officials said. Six others, including policemen and civilians, were injured in the explosion.
The blast was aimed at the security forces with one of their vehicles badly damaged. Two other vehicles were also damaged in the blast.
Today's attack appears to be the deadliest attack in Egypt since May.
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Attacks targeting police and military personnel increased after Morsi's ouster in 2013 by military following massive protests against his rule.
Over 700 security personnel have been reported killed since then.
(REOPENS FGN17)
Hours after the blast, another explosion took place in Kafr el-Shiekh in the northern part of Egypt in which a civilian was killed and two policemen were injured.
The bomb targeted a police vehicle in a village in Kafr el-Shiekh governorate.