CAIRO — An angry crowd of thousands gathered at the largest cathedral here on Monday to mourn the death of two dozen Coptic Christian demonstrators killed the night before in clashes with security forces, as liberal activists lamented the military’s increasingly tight hold on power.

The bloodshed appeared to mark a turning point in the revolution, many here said. It comes just eight months after Egyptians celebrated their military as a savior for its refusal to use force against civilians demanding the ouster of President Hosni Mubarak. Confidence in the military had already been eroded by its repeated deferrals of a handover of power to civilian rule, now set to take place perhaps as much as two years after parliamentary elections, set to begin next month.

Now political liberals as well as Copts said the brutal crackdown had finally extinguished the public’s faith in the ruling military council as the guardian of a peaceful transition to democracy.

“The credit that the military received from the people in Tahrir Square just ran out yesterday,” the party leader Ayman Nour said at a news conference of prominent parties and political leaders denouncing the military. “There is no partnership between us and the council now that the blood of our brothers stands between us.”

Others took an even darker view, saying that the violence suggested that the military may now hold an even tighter grip on power than Mr. Mubarak did.

“Cairo yesterday was a part of Syria,” said Shady el-Ghazaly Harb, a liberal activist who helped set off the revolution, invoking the violent crackdown against that country’s uprising. “This is a threat not just to the Copts, but to all of the people. We saw what would happen if we rose up against the army.”