Egyptian security forces opened fire on supporters of ousted President Mohamed Morsi, in the pre-dawn hours on Saturday, near Rabaa al-Adawiya Square in eastern Cairo, killing at least 70, the Muslim Brotherhood organization, which backs Morsi, said.

The fresh wave of violence escalated tension between the Brotherhood and Egypt’s military that's been growing ever since an army-backed interim government came to power after deposing Morsi on July 3, following nationwide protests against his government.

Security forces initially tried to disperse Morsi’s supporters, who have been staging a vigil in and around Rabaa al-Adawiya Square for the past few weeks, using tear gas, but the crowd responded by pelting stones at the troops and erecting barricades to prevent them from advancing, Turkish news agency Anadolu reported.

Brotherhood spokesman Gehad El-Haddad said security forces started shooting before pre-dawn prayers, adding: “They are not shooting to wound, they are shooting to kill,” Reuters reported.

Saad el-Hosseini, a senior Brotherhood politician, said “it is a first attempt to clear Rabaa al-Adawiya,” adding: “I have been trying to make the youth withdraw for five hours. I can't. They are saying they have paid with their blood and they do not want to retreat.”

There was no word from Egyptian authorities on Saturday’s violence, but officials at a makeshift hospital in eastern Cairo said at least 10 died early Saturday after Morsi supporters were confronted by security forces, Egypt’s Al-Ahram newspaper reported.

State news agency MENA reported that security forces launched a crackdown on Morsi’s supporters for trying to block the Six of October Bridge near Rabaa al-Adawiya.

Egypt’s health ministry said that at least nine people were killed in Egypt’s second biggest city, Alexandria, on Friday, when clashes erupted between supporters and opponents of Morsi during mass rallies across the nation. Hundreds were also injured nationwide, including at least seven policemen, according to the health ministry.

Morsi, who has been held by the army since his government was overthrown on July 3, was ordered to serve 15 days of formal detention due to a series of accusations, including killing soldiers and conspiring with Palestinian militant organization Hamas, MENA reported on Friday.