At least ten supporters of deposed president Mohamed Morsi were killed at the hands of security forces in the early hours of Saturday, said Omar Amer, a doctor at the makeshift field hospital of the pro-Morsi sit-in staged around Rabaa Al-Adawyia Mosque, Cairo's Nasr City district.
According to state news agency MENA as well as numerous accounts, police forces led a crackdown on pro-Morsi protesters for seeking to block the nearby Six of October Bridge.
Some 500 have also been injured as violence erupted near the Unknown Soldier Memorial, located nearly one km away from Rabaa Al-Adawyia Mosque, said Amer.
Speaking to Al-Jazeera Mubashir Misr, Amer said the makeshift hospital is in dire need of doctors, medications and medical equipment. Official death and injury tolls have yet to be released.
The Qatari-owned channel showed a footage of several people covered in blood as they are transferred to the field hospital amid a cloud of what seemed to be teargas. sound of sirens and gunshots are clearly heard in the background.
Karim, a 27-year-old Muslim Brotherhood member who was at scene, told Ahram Online he had witnessed police forces using both teargas and live ammunition against protesters.
Violence in Nasr City district broke out few hours following a statement by interior minister Mohamed Ibrahim, asserting that pro-Morsi sit-ins will be "dispersed by law."
For weeks, thousands of pro-Morsi protesters have been staging a sit-in near Rabaa Al-Adawyia Mosque and another at Giza's Al-Nahda Square in front of Cairo University. They have also been organising marches across Egypt to demand the reinstatement of Morsi as president.
In Nasr City, protesters are usually situated near Rabaa Al-Adawyia Mosque. However, their numbers unprecedentedly increased on Friday to reach the Unknown Soldier Memorial and approach the Six of October Bridge.
The Muslim Brotherhood, from which Morsi hails, instigated massive demonstrations on Friday to counterbalance nationwide protests called for by army chief Abdel-Fattah El-Sisi, who said he wanted to be granted popular "mandate to deal with violence and potential terrorism."
Responding to his call, millions hit the streets across the country on Friday to voice support for El-Sisi and Egypt's army, and also to chant against Morsi and the Brotherhood.
After one year in office, Morsi was ousted on 3 July as part of the Egyptian armed forces' roadmap, which was enforced shortly after nationwide mass protests against the former elected president.
Morsi has been held incommunicado ever since.
Many of Morsi's supporters and opponents have frequently faced off since his overthrow, leading to at least 100 dead and hundreds injured in the past few weeks. Both camps used against each other firearms, among other weapons, on many occasions.
The latest of these confrontations occurred Friday in Alexandria, leading to the death of at least seven protesters.