Egypt's interim president signed into law on Sunday a bill that rights groups have said sharply curbs the rights of citizens to assemble and protest peacefully.
State television reported that Adli Mansour had signed the bill, which requires protesters to receive advance permission from the police before gathering.
In the nearly three years since President Hosni Mubarak was ousted in a popular uprising, Egyptians have taken to the street regularly to air their grievances.
Rights groups had urged Mansour to reject the draft presented to him by the cabinet installed after the army overthrew President Mohamed Morsi of the Muslim Brotherhood in July.
"The draft law seeks to criminalize all forms of peaceful assembly, including demonstrations and public meetings, and gives the state free hand to disperse peaceful gatherings by use of force," read a joint statement issued on Friday by 19 Egyptian rights groups.
Thousands of supporters of the Muslim Brotherhood and Morsi were demonstrating in Cairo and in several other cities when the news was announced. They were marking the passing of 100 days since security forces dispersed two pro-Morsi sit-ins in Cairo, killing hundreds.