Five policemen were killed and 12 wounded on Thursday in blasts in Egypt's Giza province, a security source told dpa.
Two bombs apparently went off as security forces besieged a house in the area of Nazlet al-Seman where terrorist suspects were hiding, the source said.
He said the number of causalities was expected to rise.
The suspects next bombed the entire house, the source said.
Security forces cordoned off the area as ambulances rushed the injured to nearby hospitals.