A security source said three were arrested on charges of killing a policeman and wounding another during a march of supporters of President Mohamed Morsy in front of a church in Ain Shams on Wednesday.
Police allegedly found with them the murder weapon, an iron pipe stained with blood.
Authorities say the men were members of the Muslim Brotherhood.
The source also said another two members of the Brotherhood were arrested on charges of inciting demonstrations and violence.
Edited translation from Al-Masry Al-Youm