Scott Lucas has the details of the Christian march in Egypt's capital, where 24 died:

The protesters were angry at the latest attack on the Coptic Church in the village of Merinab in Aswan when Muslim villagers attempted to block renovations underway at a Christian church in the majority Muslim village, charging that the building was a "guesthouse" that cannot be turned into a church. The protesters also demanded that the governor of Aswan be removed for justifying the attack on the church and saying that a permit was not issued. The protesters were also furious at the increasing attacks against Copts in recent months and the army’s lack of protection. 

Jon Jensen parses the scene on the ground:

Just as quickly as the Copts reached their destination, a massive rock fight erupted between protesters and hundreds of "thugs" across from the television building. It was not immediately clear whether the thugs — an increasingly common catch-all for anyone instigating violence — were average citizens or plainclothes security officials. Several eyewitnesses reported that the thugs initiated the attack against Christian protesters. Egypt’s government, on the other hand, blamed the Copts for the violence.

Egypt's own Health Ministry reports 272 people were wounded: