Interim president Adly Mansour declared a state of emergency on Wednesday and imposed a curfew from 7pm to 6am, to last for one month.
The declaration followed nationwide violence following the violent dispersal of sit-ins in support of ousted president Mohamed Morsi.
A presidential statement said the decision was taken in light of “the endangered security and order throughout the nation.”
The presidency accused “extremist elements, groups and organisations” of deliberately sabotaging and attacking public and private property and killing citizens.
Mansour also authorised the armed forces to assist the police in taking all necessary measures to maintain security and order and to protect citizens and property.
According to law 162/1958, a state of emergency gives the police jurisdiction to issue administrative arrest warrants for those who “pose as a threat to general security” and to make arrests without warrants.
The law also imposes restrictions on freedom of assembly, movement and residence; and allows for exceptional trials of civilians and censorship of all media outlets.
The Al-Nahda Square sit-in in Giza was forcibly dispersed early Wednesday; protesters then moved to Mostafa Mahmoud Square in Mohandessin and set-up a new sit-in amid clashes with Central Security Forces.