At least 16 policemen were killed in a shootout with militants southwest Cairo, an Egyptian security official said Friday.
The official said the exchange of gunfire took place on Friday in the al-Wahat al-Bahriya district in the Giza governorate, about 135 kilometers, or 84 miles, from the Egyptian capital.
The number of dead was expected to rise, the source said, adding that eight other security personnel were wounded in the attack.
The official spoke on condition of anonymity because he was not authorized to talk to reporters.
Authorities were reportedly following a lead to an apartment thought to house eight suspected members of Hasm, a group which has claimed several attacks around the capital targeting judges and policemen since last year.
No militant group immediately claimed involvement in Friday's shootout.
Egypt has been under a state of emergency since bombings and suicide attacks targeting minority Coptic Christians killed scores earlier this year.