The latest eruption of political violence has deepened the malaise as Morsi struggles to get a grip on enormous social and economic problems and the increasingly dangerous fault lines that divide this nation of 85 million.
In an ominous sign, a one-time jihadist group on Sunday blamed the secular opposition for the violence and threatened to set up vigilante militias to defend the government it supports.
Addressing a news conference, Tareq el-Zomr of the once-jihadist Gamaa Islamiya, said:
"If security forces don't achieve security, it will be the right of the Egyptian people and we at the forefront to set up popular committees to protect private and public property and counter the aggression on innocent citizens."
His threat was accompanied by his charge that the opposition was responsible for the deadly violence of the past few days, setting the stage for possible bloody clashes between protesters and Islamist militiamen. The opposition denies the charge.
In Port Said on Sunday, tens of thousands of mourners poured into the streets for a mass funeral for most of the 37 people who died on Saturday. They chanted slogans against Morsi.
"We are now dead against Morsi," said Port Said activist Amira Alfy. "We will not rest now until he goes and we will not take part in the next parliamentary elections. Port Said has risen and will not allow even a semblance of normalcy to come back," she said.
The violence flared only a month after a prolonged crisis — punctuated by deadly violence — over the new constitution. Ten died in that round of unrest and hundreds were injured.
In Port Said, mourners chanted "There is no God but Allah," and "Morsi is God's enemy" as the funeral procession made its way through the city after prayers for the dead at the city's Mariam Mosque. Women clad in black led the chants, which were quickly picked up by the rest of the mourners.
There were no police or army troops in sight. But the funeral procession briefly halted after gunfire rang out. Security officials said the gunfire came from several mourners who opened fire at the Police Club next to the cemetery. Activists, however, said the gunfire first came from inside the army club, which is also close to the cemetery. Some of the mourners returned fire, which drew more shots as well as tear gas, according to witnesses. They, together with the officials, spoke on condition of anonymity because of the sensitivity of the situation in the city on the Mediterranean at the northern tip of the Suez Canal.
A total of 630 people were injured, some of them with gunshot wounds, said Abdel-Rahman Farag, director of the city's hospitals.
Also Sunday, army troops backed by armored vehicles staked out positions at key government facilities to protect state interests and try to restore order.
There was also a funeral in Cairo for two policemen killed in the Port Said violence a day earlier. Several policemen grieving for their colleagues heckled Interior Minister Mohammed Ibrahim, who is in charge of the force, when he arrived for their funeral, according to witnesses.
The angry officers screamed at the minister that he was only at the funeral for the TV cameras — a highly unusual show of dissent in Egypt, where the police force maintains military-like discipline.
Ibrahim hurriedly left and the funeral proceeded without him, a sign that the prestige of the state and its top executives were diminishing.
In Cairo, clashes broke out for the fourth straight day on Sunday, with protesters and police outside two landmark, Nile-side hotels near central Tahrir Square, birthplace of the 2011 uprising. Police fired tear gas while protesters pelted them with rocks.