CAIRO (AP) — Overnight clashes between security forces and supporters of ousted Egyptian President Mohammed Morsi in east Cairo left at least 38 protesters dead on Saturday, a doctor at the demonstrators’ field hospital said. They followed a day of massive pro-military rallies backing a tough hand against Morsi’s backers and the Muslim Brotherhood group from which he hails.

The violence close to the Morsi supporters’ month-old sit-in near the Rabaah al-Adawiyah Mosque in east Cairo is one of the deadliest bouts of violence in Egypt’s turmoil following the 2011 popular uprising. It also comes almost three weeks after more than 50 people, mostly demonstrators, died in a similar outbreak of violence outside a military installation near the same sit-in.

Doctor Yehia Mikkia said Saturday’s casualties — mostly gunshot and birdshot wounds to the upper part of the body — have overwhelmed the hospital operating from the sit-in. He said the number of death is likely to be higher because other casualties were transported to different hospitals.

The state news agency MENA quoted an unnamed senior security official saying that the security forces had not used gunfire against the protesters, only tear gas. He said security forces tried to prevent fighting between residents of the area and the protesters, and that eight members of the security forces were wounded, including some by birdshot.

The bodies of over 12 men were shrouded in white clothes, lying in pools of blood, were laid on the floor of the field hospital in images broadcast by Al-Jazeera Mubashir Misr TV. Mikkia said hundreds were wounded.