CAIRO (AFP) - President Mohamed Mursi on Sunday declared a state of emergency in three provinces hit by rioting which has left dozens dead, warning he was ready to take further steps to confront threats to Egypt's security.

Emergency measures would come into effect in the provinces of Port Said, Suez and Ismailia "for 30 days starting at midnight", Mr Mursi said in an address on state television.

Curfews would be imposed on the same three provinces from 9.00am until 6.00pm, he added.

Mr Mursi's comments came after rioting sparked by death sentences being passed on football fans for deadly violence in 2012 rocked Port Said for a second straight day on Sunday, leaving another six people dead and more than 460 injured, according to medics.

Crowds attempted to storm three police stations in the canal city and others torched a social club belonging to the armed forces, looting items inside, security officials said.

The latest casualties, among the six a teenager shot in the chest, add to the toll of 31 people including two anti-riot police killed in the Mediterranean city on Saturday.

Unrest also erupted on Sunday in Suez, another canal cisty, where protesters surrounded a police station, lobbed Molotov cocktails at security forces and blocked the road leading to the capital, security officials said.

And in the capital, clashes broke between police and protesters who accuse Mr Mursi of betraying the goals of the revolution that ousted Mr Hosni Mubarak two years ago, highlighting deep political divisions in the country now ruled by Islamists.

Clashes during the night in Cairo near Tahrir Square - symbolic heart of the 2011 uprising that toppled Mr Mubarak - continued sporadically during the day and into Sunday evening, witnesses said.

The United States and British embassies, located just minutes from Tahrir Square, closed their services to the public for the day.

Mr Mursi warned that he was ready to take further measures unless there is an end to the deadly unrest that has swept Egypt since Friday, when protests to mark the second anniversary of the anti-Mubarak revolt turned violent.

"If I must I will do much more for the sake of Egypt. This is my duty and I will not hesitate," the president warned.

A few hundred people took to the streets of Ismailiya just after Mr Mursi made his announcement and clashed with police, an Agence France-Presse correspondent said. A medical source said six people were injured.

Mr Mursi in his address also held out an olive branch to the opposition and political leaders across Egypt, inviting them for talks on Monday, saying "there is no alternative to dialogue".

He added in his brief address: "There is no going back to freedom and democracy... the rule of law and social justice that the revolution has paved".

A statement by his office later said the leaders of the National Salvation Front, the main coalition of parties and movements opposing the ruling Islamists, are among those invited to attend talks on Monday at the presidential palace.

The National Salvation Front, led by Nobel peace laureate Mohammed ElBaradei, former Arab League boss Amr Mussa and leftist politician Hamdeen Sabbahi, has warned it would "not participate" in upcoming parliamentary polls unless the causes of the violence are addressed.

The rioting in Port Said began on Saturday after a Cairo court handed down death sentences on 21 supporters of the local football club, Al-Masry, in the wake of football violence in 2012 that left 74 people dead.

Mr Mursi insisted that the verdicts that triggered the violence "must be respected by all of us". He condemned the violence as "a violation of the law and a violation of the revolution".

Residents of Port Said earlier on Sunday carried out the grim task of burying those killed the previous day, with bodies wrapped in white shrouds being carried in open coffins by a sea of mourners along the city's main avenue.

"Our city is being hit by the interior ministry!" and "Down with Brotherhood rule!" chanted the crowd, referring to the Muslim Brotherhood from which Mr Mursi draws his main support.

A brief burst of gunfire sent mourners running in several directions amid chaotic scenes, which later degenerated into rioting again.

Egypt was under a state of emergency for more than three decades in the wake of the assassination of president Anwar Sadat in 1981 and until May last year, a month before the election of Mr Mursi.

Ending the state of emergency - which allowed authorities to detain people without charge and them them in emergency security courts - was a key demand of protesters who toppled Mr Mubarak in 2011.