Supporters of Hazem Salah Abu Ismail, who are staging a Tahrir Square sit-in to demand the removal of the supplement to the Constitutional Declaration, clashed with people directing traffic on Saturday.
The people directing traffic had allowed cars to be parked near the protesters' tents, erected in the middle of the square.
Abu Ismail is a Salafi leader and was a presidential candidate in the recent elections, before being disqualified as his late mother held American nationality.
Different clashes erupted between street vendors and other people in Tahrir Square, also on Saturday, because of disagreements over the price of the goods being sold. A street vendor suffered a cut to the head and was taken to Qasr al-Aini Hospital.
A number of street vendors have established cafes next to the Mugamma, a large administrative building in the square, to host those visiting the area after iftar, the meal the breaks the Ramadan fast.
The square retured to calm by the afternoon.
Edited translation from Al-Masry Al-Youm