CAIRO – Egyptian security forces backed by water cannons fired tear gas at rock-throwing protesters outside the presidential palace in Cairo on Friday while demonstrators clashed with riot police in cities across the country in marches against Islamist President Mohammed Morsi.

The protests are part of a wave of opposition-led demonstrations over the past two weeks that have frequently devolved into street clashes. The violence has left more than 70 people dead and hundreds wounded, and plunged the country into a fresh cycle of bloodshed and political turmoil.

Egypt’s opposition is demanding Morsi form a new coalition government, open an investigation into the killings of protesters over the past months and give guarantees that upcoming parliamentary elections will be fair and free. They also want him to form a commission to amend the country’s newly adopted constitution, which was drafted by an Islamist-led panel and approved last December in a contentious referendum.

Some of the protesters go even further, demanding Morsi be removed from office. They also accuse the Muslim Brotherhood, the fundamentalist group from which Morsi hails, of monopolizing power and failing to deal with the country’s mounting woes.

Thousands took their demands to the streets in cities across the country on Friday, carrying Egyptian flags and pictures of slain protesters and chanting “down with the rule of the Guide,” referring to Brotherhood Supreme Guide Mohammed Badie, who critics allege is calling the shots for Morsi from behind the scenes.

At the presidential palace in Cairo, the scene of repeated violent clashes since late last year, protesters tried to remove the barbed wire at the front gate of the palace and fired flares at its perimeters. Riot police swiftly responded with water cannons and tear gas while protesters hurled stones.

Violence also broke out in Kafr el-Sheik, some 110 miles north of Cairo, where riot police clashed with protesters in front of the office of governor Saad el-Husseini, who is a member of the Muslim Brotherhood.

In the Mediterranean port city of Alexandria, protesters tore down a Brotherhood sign and burned it in front of the group’s office while security forces used tear gas to disperse demonstrators in front of the governor’s office.

Morsi and his allies accuse the opposition of trying to incite street violence to seize power after failing at the ballot box.