Supporters of Egypt's ousted President Mohammed Morsi carry a wounded man during clashes with Egyptian security forces in Ramses Square, Cairo, Egypt, Friday, Aug. 16, 2013. Supporters of Egypt's ousted President Mohammed Morsi carry a wounded man during clashes with Egyptian security forces in Ramses Square, downtown Cairo, Egypt, Friday, Aug. 16, 2013. Supporters of Egypt's ousted President Mohammed Morsi clash with Egyptian security forces in Ramses Square, downtown Cairo, Egypt, Friday, Aug. 16, 2013. CAIRO (AP) - Egypt's capital descended into chaos Friday as vigilantes at neighborhood checkpoints battled Muslim Brotherhood-led protesters denouncing the ouster of President Mohammed Morsi and a deadly crackdown. The fiercest street clashes Cairo has seen in more than two years of turmoil left at least 82 people dead, including 10 policemen. The sight of residents firing at one another marked a dark turn in the conflict, as civilians armed with pistols and assault rifles fought protesters taking part in what the Muslim Brotherhood called a "Day of Rage" - ignited by anger at security forces for clearing two sit-in demonstrations Wednesday that sparked nationwide clashes in which more than 600 people died. Military helicopters circled overhead as residents furious with the Brotherhood protests pelted marchers with rocks and glass bottles. The two sides also fired on one another, sparking running street battles throughout the capital's residential neighborhoods. Across the country, at least 72 civilians were killed, along with 10 police officers, security officials said, speaking on condition of anonymity in line with regulations. Friday's violence capped off a week that saw more than 700 people killed across the country - surpassing the combined death toll from two and a half years of violent protests since the ouster of longtime leader Hosni Mubarak until the toppling of Morsi in a July 3 coup. Unlike in past clashes between protesters and police, Friday's violence introduced a combustible new mix, with residents and police in civilian clothing battling those participating in the Brotherhood-led marches. Few police in uniform were seen as neighborhood watchdogs and pro-Morsi protesters fired at one another for hours on a bridge that crosses over Cairo's Zamalek district, an upscale island neighborhood where many foreigners and ambassadors reside. Friday's violence erupted shortly after midday prayers when tens of thousands of Brotherhood supporters answered the group's call to protest across Egypt in defiance of a military-imposed state of emergency following the bloodshed earlier this week. At one, residents barred ambulances and cars carrying wounded from Cairo's main battleground, Ramses Square, from reaching a hospital. By choosing Ramses Square as the focus of Friday's demonstrations, the Brotherhood appeared to be trying to establish another protest site to replace the two forcibly cleared Wednesday - but this time in an area that cuts through the heart of Cairo. The area is near Tahrir Square, where the army put up barbed wire and deployed 30 tanks outside the Egyptian Museum overlooking the area as a buffer between the protesters and a small anti-Brotherhood encampment in the square. Several of the protesters said they were ready to die, writing their names and relatives' phone numbers on one another's chests and undershirts in case they were killed in Friday's clashes. Tawfik Dessouki, a Brotherhood supporter, said he was fighting for "democracy" and against the military's ouster of Morsi. We didn't have a revolution to go back to a police and military state again and to be killed by the state," he said during a march headed toward Ramses Square. Heavy gunfire rang out over a main overpass where pro-Morsi protesters were marching toward Ramses Square. Video online showed protesters trying to flee the bullets, with at least one person jumping off the high overpass and others hanging off the side. Some used a rope to get down. It was not immediately clear where the bullets were being shot from. Alia Mostafa of the Anti-coup Alliance, a group that works closely with the Brotherhood, said snipers were shooting down at protesters in the Ramses Square area. "Police are firing live ammunition from the roof tops of the nearby police station," she said. At least 12 people were killed near the square as some in the crowd tried to attack a police station, security officials said. Inside Al-Fath mosque near Ramses Square, where the Brotherhood urged its Cairo supporters to converge, blood-soaked bodies with bullets to the head and chest lay next to one another. The mosque-turned-morgue was also being used as a field hospital where the wounded were being wheeled in on wooden crates. One corpse had a name and phone number scribbled on the chest. The Facebook page of the army spokesman, Col. Mohammed Ali, accused gunmen of firing from the mosque at nearby buildings. The upper floors of a commercial building towering over Ramses Square caught fire during the mayhem, with flames engulfing it for hours. Dozens of protesters remained in the mosque overnight and military and police forces surrounded the area, raising fears a raid could lead to more bloodshed. There was little hope that an evening curfew would curb the violence as the Muslim Brotherhood called on Morsi's supporters to stage daily protests. Friday's violence highlighted how dangerous the divisions in Egypt have become as similar battles played out in cities across the country, where people brandishing weapons attacked police and residents fired at one another. Gunmen targeted police check points and at least 10 police stations came under attack. Egypt's security forces were rocked by the country's 2011 uprising that toppled Mubarak and have not fully recovered since. In the canal city of Suez, 14 people were killed in clashes between protesters and security forces. In Egypt's second-largest city of Alexandria, 10 people were killed during clashes between the two rival camps. Security officials said violence was also fierce in the province of Fayoum, just west of Cairo, where seven people were killed during an attempt to storm the main security building there, a security official said. Two policemen died in the attack. In the southern province of Minya, protesters attacked two Christian churches, security officials said. At churches across the country, residents formed human chains to try to protect them from further assaults, and a civilian was killed while trying to protect a church in Sohag, south of Cairo, authorities said. Many of Morsi's supporters have criticized Egypt's Christian minority for largely supporting the military's decision to remove him from office, and dozens of churches have been attacked this week. Mourad Ali, a spokesman for the Brotherhood, denounced the attacks on churches, saying they ran counter to Islamic principles and were an attempt to ignite sectarian divisions. Our stance is clear ... We strongly condemn any attack - even verbal - on churches and on Coptic property. This holds true whether or not Coptic leaders joined in or supported the July 3 coup ... This does not justify any attack on them," he said in an online statement. More than 800 people were arrested in Friday's clashes, including local Brotherhood leaders in the provinces. The group's top figures are facing charges of inciting violence and some have been imprisoned for weeks. Morsi has been held at an undisclosed location and is facing a criminal investigation. Morsi, a longtime Brotherhood leader, was ousted by the military after days of mass protests against him. He was accused by his critics of failing to govern inclusively and Cairo witnessed street clashes between his supporters and opponents on at least three occasions during his year in office, though the fighting was confined to key areas of the capital and not nearly as fierce or deadly as Friday's violence. The revolutionary and liberal groups that helped topple Morsi have largely stayed away from the street rallies in recent weeks. The Popular Current, a leftist anti-Morsi group, said they were "astounded" by how some in the international community have denounced Wednesday's move against the Islamist protest camps as "state violence against civilians." The statement reflected widespread sentiment that the Cairo sit-ins had to be dispersed after the government issued warnings to protesters over the past several weeks. The government, bolstered by wealthy Arab Gulf states opposed to the Brotherhood, has branded the crackdown on Islamists as part of a wider fight against "terrorists." Saudi Arabia's King Abdullah, whose country has pledged $5 billion in aid to interim leaders in Egypt, said the kingdom stood by the country in its fight against "terrorism and strife" - a thinly veiled reference to the Brotherhood. Egypt's military-backed government released a statement Friday accusing "terrorist groups" and "outlaws" of confronting security forces, which it said must "stand together against a terrorist plot." The interim Cabinet authorized police to use of deadly force against anyone targeting police and state institutions a day earlier. Egyptian state television showed footage of armed Brotherhood supporters under the banner headline "Egypt Fights Terrorism." The Brotherhood's political wing, the Freedom and Justice Party, said in a statement Friday that the group is not backing down. "We are not only dealing with the disbandment of a sit-in, but with the extermination of the Egyptian people to subject them to military rule with steel and fire," the group said in a statement, warning that differences will deepen. The international community has urged both sides to show restraint and end the turmoil engulfing the nation. The European Union's foreign policy chief Catherine Ashton said Friday that the death toll over the last few days is "shocking" and that responsibility weighs heavily on the interim government and the wider political leadership in Egypt.