ASSIUT, Egypt — It was nighttime and 10,000 Islamists were marching down the most heavily Christian street in this ancient Egyptian city, chanting “Islamic, Islamic, despite the Christians.” A half-dozen kids were spray-painting “Boycott the Christians” on walls, supervised by an adult.

While Islamists are on the defensive in Cairo following the military coup that ousted President Mohammed Morsi, in Assiut and elsewhere in Egypt’s deep south they are waging a stepped-up hate campaign, claiming the country’s Christian minority somehow engineered Morsi’s downfall.

“Tawadros is a dog,” says a spray-painted insult, referring to Pope Tawadros II, patriarch of the Copts, as Egypt’s Christians are called. Christian homes, stores and places of worship have been marked with large painted crosses.

The hostility led a coalition of 16 Egyptian rights groups to warn on Wednesday of a wave of violence to come, and to demand that the post-coup authorities protect the Christians who are 10 percent of the population and suffer chronic discrimination.

Nile-side Assiut, a city of one million people 250 miles south of Cairo, dates back to the pharaohs. The New Testament says Mary, Joseph and the infant Jesus passed through as they fled the infanticidal King Herod. Today, its Christian fears are compounded by the failure of authorities to curb the graffiti-spraying and the Islamists’ demonstrations, which have gone on almost nightly since the July 3 coup that ousted Morsi.

“They (the Islamists) will not stop as long as they are left to do as they please without fear of accountability,” said Hossam Nabil, 38, who owns a jewelry store where the demonstration passed on Tuesday night. “They are many and one day they will trash our stores.”

Like other Christians with stores on the street, Nabil shuttered his establishment until the protesters had passed. “They (the marchers) run their index finger across their throats to suggest they will slaughter us, or scream Morsi’s name in our faces,” he said.

A young couple arrived to shop while scores of marchers were still on the street. They froze in fear, the husband shielding his wife with his body.

Families living in apartment blocks above the stores stayed home, shutting windows and staying off balconies. Those outdoors kept their distance from the march.

Assiut’s Islamists are strong because local authority is weak and religion is powerful in a region where poverty is widespread and envy of the relatively high number of well-to-do Christians runs high.

As for the graffiti, acting provincial governor Gamal Adam told The Associated Press the authorities have given up on washing it away because it quickly reappears.

For the 40 percent of Assiut people who are Christian, life has changed radically. They find their apartment blocks disfigured by painted crosses with a red X painted over them. They stay at home at night. Churches have canceled afternoon activities. Some of the wealthy have left town.