Egyptian President Mohammed Morsi has declared a state of emergency in the cities of Port Said, Suez and Ismalia after days of deadly unrest.
A daily curfew from 21:00 to 06:00 will be imposed for 30 days from Monday, he said in a speech to the nation.
At least 33 people died over the weekend in Port Said, where a court judgment sparked rioting.
Unhappiness with Mr Morsi’s rule fuelled unrest elsewhere.
In the capital Cairo, anti-government protesters clashed with security forces near Tahrir Square for a fourth consecutive day.
The liberal opposition accuses Mr Morsi of being autocratic and driving through a new constitution that does not protect adequately freedom of expression or religion.
The government is also being blamed for a deepening economic crisis.
Mr Morsi said he might take further steps "for the sake of Egypt" as it was his "duty" as president.
He also invited political leaders to a "national dialogue" on Monday.
State of rage
The state of emergency applies to the three cities along the Suez Canal, and their surrounding regions.
"I have said I am against any emergency measures but I have said that if I must stop bloodshed and protect the people then I will act," the president said.
"If I must I will do much more for the sake of Egypt. This is my duty and I will not hesitate."
Protests erupted in Port Said after a court sentenced 21 local people over deadly football violence nearly a year ago.