Saturday's attack on the Church of The Two Saints in Alexandria after a New Year's mass attended by 1,000 people, killed 21 people and wounded 79, the worst such outrage since 1999 but one of many.
As Copts clashed with police in violent protests, Egyptian newspapers warned that "civil war" could erupt unless Christians and Muslims closed ranks.
Egyptian President Hosni Mubarak blamed "foreign hands" for the bombing in the Mediterranean city founded by Alexander the Great in 331 B.C., a reference to al-Qaida which is waging a campaign of violence against Christians in Iraq.
But that's a kneejerk response by a government that often blames the country's misfortunes on outsiders.
Counterterrorism experts said it is more likely that the attack was the work of Islamic extremists in Egypt, possibly remnants of the Islamist groups who waged a five-year insurgency against Mubarak's regime in the 1990s before they were ruthlessly crushed.
One of the leaders of that insurgency, Anwar al-Zawahiri, a physician from a wealthy Cairene family, fled to Afghanistan and founded al-Qaida with Osama bin Laden.
Sectarianism has been growing of late, the consequence of the Islamic resurgence across the Muslim world and increasingly intense competition for dwindling national resources.
Still, British author Hugh Miles, who specializes in Egyptian affairs, doesn't foresee conflict along religious lines.
"An Iraq-style sectarian war is not likely in Egypt as the vast security forces have an iron grip on the country, enjoy the full support of the West and have the rare distinction of having successfully ended a violent insurgency by Islamic extremists in the past, albeit by using fairly brutal methods," he said.
But he conceded that there is a danger "that is such a repressive country, the kind of violent and angry protests that came in the wake of this attack can seamlessly dovetail with anti-government feelings, leading to civil unrest."
Saturday's atrocity occurred at a time of mounting political instability in Egypt, which is facing a contentious presidential election in a few months and a leadership succession problem that could provoke nationwide turmoil.
Mubarak, 82 and in failing health, has ruled as president since October 1981, when he took over from Anwar Sadat, assassinated by Islamist extremists for making peace with Israel in 1979.
Mubarak has held onto office through highly suspect elections, in which opposition candidates were ruthlessly sabotaged. He has ruled with emergency powers declared when Sadat was shot to death.
The opposition, including the relatively moderate Muslim Brotherhood, fears he's preparing to install his business tycoon son, Gamal, already promoted to high office in the ruling National Democratic Party, as his successor.
Mubarak needs the backing of the military to do that and so far it hasn't been forthcoming.
But any move, dynastic or not, that perpetuates the regime is likely to ignite mass protests and possibly violence that would play into the hands of Islamic extremists.
The Copts comprise 10 percent of Egypt's population of 82 million, making them the largest Christian community in the Arab world. Although many Copts have become Cabinet ministers and business magnates, the Christians complain of discrimination.
Before the 1952 revolution led by Gamal Abdel Nasser that overthrew the corrupt monarchy, Copts were 20 percent of the population and controlled nearly half the country's wealth. But when Nasser imposed socialist policies, many left as much of their wealth was seized by the state.
The Alexandria bombing came amid growing alarm about the fate of dwindling Christian communities across the Middle East, driven out by Muslim violence, political strife and persecution.
In recent months, al-Qaida's affiliate in Iraq has waged a campaign of killings and bombings against one of the oldest Christian communities in the world.
It warned Egypt's Copts to release two priests' wives it said were "imprisoned in their monasteries" for converting to Islam so they could get divorces, which are banned by the Orthodox Coptic Church.
The Coptic Church denied that but the fate of the two women has become something of an urban myth among militant Muslims and further attacks are entirely possible.