While no one has claimed responsibility for the attack, Egypt has been fighting an insurgency by a local affiliate of the so-called Islamic State group in North Sinai province.
Hundreds of soldiers and policemen have been killed in the insurgency since the army overthrew Islamist president Mohamed Morsi in 2013.
Following deadly church bombings last month, President Abdel Fattah al-Sisi declared a three-month state of emergency on April 10.
The so-called Islamic State group said it was behind the church bombings in Tanta and Alexandria on April 9 that killed 45 people.
The military has killed several of the group's top leaders, but the extremists have increasingly expanded their attacks from Sinai to other parts of Egypt, including Cairo.
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