CAIRO - Egyptians remained deeply divided over the future of their country Sunday, with no sign of an end to clashes between rivals groups that left at least 72 dead on Saturday.
Supporters of the Muslim Brotherhood said they would not leave the streets despite what they called "massacres" by security forces that shot dozens of them dead.
The spiral of violence has become so bad that Secretary of State John Kerry said Egypt is at "a pivotal moment" more than two years since the uprising ousted the longtime President Hosni Mubarak.
In a statement released Saturday, Kerry said Egypt’s military and interim rulers "have a moral and legal obligation" to respect the right of peaceful assembly and freedom of expression.
He added that the continued violence sets back efforts of "reconciliation and democratization," and affects regional stability.
Also on Saturday, Secretary of Defense Chuck Hagel spoke by phone with Army chief Gen. Abdel Fattah al-Sisi to express deep concern about the security situation and to encourage that restraint be exercised during this "difficult period."
"The United States believes that the current transition needs to be marked by inclusivity, that Egyptian authorities should avoid politicized arrests and detentions, and take steps to prevent further bloodshed and loss of life," Pentagon press secretary George Little said.
Egypt's ambulance service said 72 people were killed in Saturday's violence at a Cairo vigil by backers of deposed President Mohammed Morsi, Reuters reported.
"They will not be content until they bring back everything from the era of the corrupt, murderous security and intelligence state," senior Brotherhood official Essam el-Erian said on Facebook. "They've stepped up their efforts to do so by committing massacres never before seen in Egyptian history."
The Interior Ministry has rejected eyewitness accounts that police opened fire on the crowds and a public prosecutor has launched a probe into the violence, investigating 72 suspects for an array of crimes including murder and blocking streets, Reuters said.
Opinion remains bitterly divided about the violence, and who is to blame.
“What happened violates all religions, laws and common practices,” said Ahmed Farouk, 43, a scientific researcher. “The police and military have all the tools at their disposal to prove their innocence.”
“Every action has a reaction,” he added. “Who did the first action?”
Omayma Idriss, a gynecologist in his 50s, described Morsi supporters as “terrorists” and said the killings were carried out by their own side. “Of course, of course, they did it themselves,” he said.
“I wasn't happy with the army,” said Sahar Mohamed, 35. “We must settle things peacefully. They should have used tear gas, but never live ammunition.”
Taxi driver Hossam Said, 28, said he did not believe the claims of Muslim Brotherhood supporters who brandished shells as evidence they had been attacked by the army.
"It doesn't make any sense,” he said. “How can the person who is shooting at you be half a kilometer away and yet you have the shells? I was in the army and the maximum a shell would go is 20 meters.
"I don't know how some in the back would get shot while some in front were not. I don't know who killed them."
When asked if the army and police should clear Egypt’s squares of pro-Morsi protesters, or let them express their views, he said: "What freedom of expression, what do they have to say? They tried and failed."
Reuters contributed to this report.