Egyptian President Mohamed Morsi has declared a state of emergency in three Suez Canal cities hit by rioting which has left dozens dead.
In an address on state television, Mr Morsi said the emergency measures, which include night curfews, would be in place in Port Said, Suez and Ismailia for 30 days.
"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," he said.
Curfews would be imposed on the three provinces from 9pm until 6am, he added - and he warned he would take further steps to confront threats to Egypt's security if need be.
Mr Morsi acted after a second day of rioting rocked Port Said on Sunday. The violence left six people dead and more than 460 injured, according to medics.
"If I must I will do much more for the sake of Egypt. This is my duty and I will not hesitate," he said.
He also held out an olive branch to the opposition and political leaders across Egypt, inviting them for talks later today, saying "there is no alternative to dialogue".
The opposition threatened to boycott upcoming parliamentary polls if Mr Morsi did not find a "comprehensive solution" to the unrest.
The worst violence this weekend was in the Mediterranean coastal city Port Said, where at least 44 people have been killed in clashes that started on Saturday.
The violence was sparked by a court conviction and death sentence for 21 football fans involved in a riot at the city's main stadium that left 74 dead last year.
Most of those sentenced to death were from Port Said, deepening a sense of persecution that the city's residents have felt since the stadium disaster.
Crowds attempted to storm three police stations in Port Said and others torched a social club belonging to the armed forces, looting items inside, security officials said.
Unrest also erupted on Sunday in Suez, where protesters surrounded a police station, attacked security forces and blocked the road leading to the capital, officials said.
At least another 11 died elsewhere in the country on Friday during rallies marking the second anniversary of the uprising that toppled authoritarian president Hosni Mubarak.
In Cairo, overnight clashes on the outskirts of Tahrir Square - the symbolic heart of the uprising against Mubarak - continued into late Sunday afternoon, with one bridge blocked off and the heavy smell of tear gas hanging in the air.
Protesters used the anniversary to renounce Mr Morsi and his Islamic fundamentalist group, the Muslim Brotherhood, which emerged as the country's most dominant political force after Mubarak was toppled.
Ending the state of emergency - which allowed authorities to detain people without charge and try them in emergency security courts - was a key demand of protesters who ousted Mubarak in 2011.