Cairo is convulsed by deadly gun battles this evening as the consequences of Wednesday’s mass killings reverberated around the country.

With army helicopters hovering high over the city centre and security services marshalling firepower to continue their bloody crackdown, Egypt looked in danger of sinking into greater violence.

Last night there was no confirmed death toll, but dozens of civilians were reported to have been killed. The violence spread across the country, with deaths reported in numerous provinces, including eight in Damietta, and four in Ismailia.

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“The army and the police are killing their own people,” said Mohamed Mahmoud, an Islamist who had made his way to central Cairo for a rally. With bursts of machine-gun fire rattling around the central train station, he told The Independent that “this is not our country any more”.

The worst violence erupted in Ramses Square, the sprawling plaza in central Cairo which had been the focus of demonstrations called by supporters of toppled President Mohamed Morsi. But in a sign that the civil unrest which has gripped Egypt for much of the past two years may have reached a tipping point, other neighbourhoods were also caught up in the chaos.

Garden City, the leafy Nileside enclave dreamed up by British colonialists, was echoing to the sound of gunfire last night. Residents shuttered windows as security services carried out operations. Witnesses also reported hearing gunfire in Zamalek, the plush upper-class island which is home to a Hilton hotel.

Many Egyptians had woken up yesterday bracing themselves for the worst. Allies of Mr Morsi had called for dozens of demonstrations, with a week of daily rallies planned across Egypt. One Brotherhood leader warned that the level of anger was such that his organisation could no longer control its followers. The interior ministry, meanwhile, issued a statement that police had been authorised to use lethal force against protesters who threatened state buildings.

Even for a Friday morning – the Muslim day of rest – the streets were quiet. Soldiers in Tahrir Square, the crucible of a revolution, sat expectantly behind their gun turrets. At around 1pm, after several thousand Islamist protesters had reached Ramses Square, shots rang out from the direction of a police station in a road leading off the plaza. At times, the bursts of gunfire were intense. Palls of smoke from burning debris added to the confusion. A young boy, perhaps only 16, was raced to a field clinic with a chunk the size of an orange slice missing from his forehead.

“The government calls all these people terrorists,” shouted Mohamed al-Adawy, 30, gesturing to the thousands of protesters packed inside the square. “They are not terrorists. They are teachers, or engineers and come from all walks of life.”

At al-Tawheed Mosque, about half a mile east of Ramses Square, shawl-wrapped corpses were lined up one by one. Inside the prayer hall down below, doctors frantically performed CPR on dying patients. “The police don’t have any humanity,” said Dr Hassan Sulayman. “They have killed people like animals.”