CAIRO/PORT SAID, Egypt - Thousands of opponents of President Mohamed Morsi returned to the streets of Egypt on Friday, demanding his overthrow after the deadliest violence of his seven months in power.

Men in black shirts of mourning marched through the Suez Canal city of Port Said, scene of the worst bloodshed of the past 9 days, chanting and shaking fists.

"There is no God but God and Mohamed Morsi is the enemy of God," they chanted. Holding aloft portraits of those killed in the latest violence, they shouted: "We will die like they did, to get justice!"

Protests marking the second anniversary of the uprising that toppled Hosni Mubarak have killed nearly 60 people since January 25, prompting the head of the army to warn this week that the state was on the verge of collapse.

For the Port Said marchers, Friday was also the first anniversary of a soccer stadium riot that killed 70 people last year. Death sentences handed down on Saturday against 21 Port Said people over the riots fueled the past week's violence there, which saw dozens shot dead in clashes with police.

Morsi imposed a curfew and emergency rule in Port Said and two other canal cities on Sunday, a move that only seems to have added to the sense of grievance there.

Protesters also marched in Alexandria, Ismailia and the capital Cairo, where they were expected to descend on the presidential palace. Morsi's supporters have clashed with protesters at the palace in the past, although the Brotherhood has kept its men off the streets in recent days.

The protesters accuse Morsi of betraying the spirit of the revolution by concentrating too much power in his own hands and those of his Muslim Brotherhood. The Brotherhood accuses the opposition of trying to overthrow the first democratically elected leader in Egypt's 7,000-year history.

Friday's marches took place despite an intervention by Sheikh Ahmed al-Tayyeb, head of the 1,000-year-old al-Azhar university and mosque, who hauled in rival political leaders for crisis talks on Thursday and persuaded them to sign a charter disavowing violence. Anti-Morsi politicians said that pact did not require them to call off demonstrations.

"We brought down the Mubarak regime with a peaceful revolution and are determined to realize the same goals in the same way, regardless of the sacrifices or the barbaric oppression," tweeted Mohamed ElBaradei, a former head of the UN nuclear watchdog who has become a secularist leader.

In a statement released overnight, leftist leader Hamdeen Sabahi said despite the Azhar initiative he would not enter talks until bloodshed was halted, a state of emergency lifted and those to blame for the violence brought to justice.

"Our aim ... is to complete the goals of the glorious January revolution: bread, freedom and social justice," he said.

The rise of Morsi, an elected Islamist, after generations of rule by authoritarian, secular military men in the most populous Arab state, is probably the single most important change of the past two years of Arab popular revolts.

But seven months since taking power after a narrow election victory over a former general, Morsi has failed to unite Egyptians and protests have made the country seem all but ungovernable. The instability has worsened an economic crisis, forcing Cairo to drain currency reserves to prop up its pound.

It is far from clear that opposition politicians could call off the street demonstrations, even if they wanted to. The protest movement has become a spontaneous expression of rage, often only loosely allied to secularist and liberal parties.

"You have groups who clearly just want a confrontation with the state - straightforward anarchy; you've got people who supported the original ideals of the revolution and feel those ideals have been betrayed," said a diplomat. "And then you have elements of the old regime who have it in their interests to foster insecurity and instability. It is an unhealthy alliance."

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