CAIRO — A demonstration by Christians angry about a recent attack on a church touched off a night of violent protests here against the military council now ruling Egypt, leaving 24 people dead and more than 200 wounded in the worst spasm of violence since the ouster of President Hosni Mubarak in February.

The sectarian protest appeared to catch fire because it was aimed squarely at the military council that has ruled Egypt since the revolution, at a moment when the military’s latest delay in turning over power has led to a spike in public distrust of its authority.

When the clashes broke out, some Muslims ran into the streets to help defend the Christians against the police, while others said they had come out to help the army quell the protests in the name of stability, turning what started as a march about a church into a chaotic battle over military rule and Egypt’s future.

Nada el-Shazly, 27, who was wearing a surgical mask to deflect the tear gas, said she came out because she heard state television urge “honest Egyptians” to turn out to protect the soldiers from Christian protesters, even though she knew some of her fellow Muslims had marched with the Christians to protest the military’s continued hold on power.