At least 25 off-duty Egyptian police officers were slaughtered in an ambush by armed militia as they were travelling in two mini-buses through a village near the border town of Rafah on the Sinai Peninsula on Monday.

According to different reports coming from that country, the officers were forced from the bus and shot as they lay face-down on the ground. Other reports say that rocket propelled grenades were used to attack the bus and the officers were killed in the resulting explosion.

This newest violence occurred one day after 36 Islamic prisoners were shot and killed during a riot and an alleged escape attempt as the prisoners were being transported between prisons north of Cairo. The Muslim Brotherhood has called for an independent investigation into that incident.

The killing of the officers is believed to have been carried out by a militant Islamic militia that deposed leader Mohamed Morsi allowed to operate in the Sinai. Morsi was deposed on July 3rd.

The news of the officers’ death came at the same time that news was aired that former Egyptian president Hosni Mubarak may be released from prison later this week. The 85-year-old former leader has been held in detention since April of 2011. He was earlier found guilty of not stopping the killings of over 900 protesters during the 18-day uprising protesting his rule. The verdict in that case was overturned on appeal. Officials say that he is being released because the two-year limit on holding a prisoner in custody pending a final verdict has expired.

Another police officer was shot and killed as he stood guard outside a bank in el-Arish on the northern Sinai a few hours after the ambush attack. That killing is also suspected to have been carried out by Islamic militants.

Over 900 people have been killed since the violence in Egypt erupted last week.