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 rageThe 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.Correspondents say the city remains in a state of rage after the 21 defendants were sentenced over riots which killed 74 people after a football game last February.February's violence began when fans of Port Said side al-Masry attacked visiting supporters from Cairo club al-Ahly.Fans flooded on to pitch attacking Ahly players and fans as the match ended.Most of the victims died of concussion, cuts and suffocation.About 30 people were killed in unrest in the city on Saturday with a further three dying at a mass funeral on Sunday.