Since the Egyptian military ousted president Mohamed Morsi from power on July 3, his supporters have gathered at two sites in the country's capital demanding his reinstatement.
The protesters, led by Mr. Morsi's Muslim Brotherhood, do not recognize the interim government the military installed. The military has announced plans for reforms and new elections.
The military's actions followed demonstrations by Mr. Morsi's opponents, who accused him of betraying Egypt's 2011 revolution.
The standoff has raised tensions in Egypt, and led to violence that has left more than 250 people dead.
The country's interim leaders portrayed the pro-Morsi protesters as dangerous radicals and called for them to leave their camps.
Early Wednesday, security forces began to clear the camps with tear gas and military vehicles.
In response, the protesters fortified the area, putting up barricades and sand bags to try to prevent security forces from entering the sites. Thousands of people, including children have been staying at the camps.