Egypt shaken by deadly Cairo clashes
The attack in the Imbaba district of Cairo has profoundly shaken Egypt.
Twelve people died and more than 200 were injured as Muslims clashed with Christians on Saturday, and two churches were set ablaze.
It followed several similar incidents and has brought home to Egyptians that the post-revolutionary era will not necessarily bring an end to religious strife.
Often, post-revolutionary environments allow conflicts to flare up, not die down.
The government reflected the seriousness of the attack by calling an emergency cabinet meeting.
It promised tough action - an "iron hand" - against those who attacked places of worship. In future they could face the death penalty.
But Egyptians have heard this before. After the last big sectarian clash in Cairo in March, which killed 13 people, military authorities talked of draconian punishments for what it called "thuggery".
That did not deter an angry crowd led by conservative Salafi Muslims from surrounding a church in Imbaba in which they believed an Islamic convert was being held against her will.
The response of the armed forces has been widely criticised.
Eyewitnesses describe dozens of soldiers, police and armoured vehicles taking position in front of the church from early evening.
At times they fired shots in the air, and some tear gas, but they were unable to prevent the Salafi protest from escalating into a deadly confrontation.
Some Christians have accused the army of being reluctant to take action.
"It is their responsibility to protect everybody, Egyptian or non-Egyptian, Muslim or Christian," said Fady Geris, a young Christian who joined a protest at the state TV office in Cairo against the lack of security.
So was the military simply unable to control the crowd, or unwilling?
Troops are not trained for this role, and during the uprising against President Mubarak they mostly chose not to confront the demonstrators, a factor that enabled the armed forces to retain its credibility.
But since then military forces have moved decisively to put down number of protests, using force.
Emad Gad, from the Al-Ahram Centre for Political and Strategic Studies, believes they have to accept responsibility for Saturday's events.
"They could control the situation if they wanted to," he says.
"They should apply the law objectively. They allowed 3,000 Islamic militants, supporters of Bin Laden, to come back here without any investigation. Now we are all suffering from this."
He was referring to a decision by the new government to end the blacklist of jihadist Muslims, allowing them to return from exile.
Salafi groups, whose activities were tightly proscribed and were kept low-profile during Mr Mubarak's rule, have suddenly become very visible.
They are alleged to have been behind a protest in the southern city of Qena last month which forced the dismissal of a Christian governor, and they have taken up the cause of women whom they believe are being prevented from converting to Islam.
Their protests are especially provocative in poorer areas, like Imbaba, where localised quarrels are commonplace between the Muslims and Christians, living cheek-by-jowl.
Emad Gad is not alone in believing that it suits the military to see communal conflict breaking out. He is also not alone in suspecting that Saudi Arabia is funding the Salafis.
"I believe there is co-operation between Saudi Arabia and the Supreme Council of the Armed Forces to make this revolution very bloody, to prevent the prosecution of Mubarak, and send a message to the rest of the Arab people that if they want to start a revolution and remove a leader, it will end like Egypt," he says.
This is impossible to prove but many Egyptians believe it.
However, those who attacked the church and nearby Christian shops were not all Salafis. Some were local young men.
Witnesses say they believe there were also members of the now-disbanded secret police in the crowd, remnants of the old regime possibly inciting violence.
Some Salafi leaders have disowned the violence, saying it "does not reflect Salafi thought".
Retired General Sameh Seif El-Yazal believes people are being too harsh on the military.
"The Supreme Council of the Armed Forces does not operate the country on a daily basis, the prime minister and the cabinet do that," he says.
"The government has to show people that they are strong. Their first priority should be to make people feel secure."
The revolution has left Egypt in something of a political and a security vacuum.
The ruling military council takes decisions in secrecy, leaving Egyptians mystified by its motives.
The government is struggling with multiple challenges - meeting huge expectations, reviving a sinking economy and managing a rushed timetable for new elections.
The police, demoralised and discredited from their past repression, are not yet fully operational.
Throw into that vacuum myriad groups now able to express long-pent-up grievances openly on the streets, and more conflicts are almost inevitable, whatever punishments are threatened.