The latest sectarian violence in Iraq has made many Iraqis more fearful than ever before that their country is falling apart and sliding towards civil strife.
The 18 bodies were found dumped in the Iraqi capital, Baghdad
The discovery of the bodies of 18 men, blindfolded and with hands bound, in the west Baghdad suburb of al-Amriya, is the latest in an apparently tightening cycle of sectarian reprisals and revenge killings between Sunnis and Shias.
In the past, many such mass killings have been blamed by Sunni groups on Shia militia death squads operating under the wing of the Interior Ministry and its security forces - a charge denied by the authorities.
The Shias have long borne the brunt of the Sunni-based insurgency, with many thousands killed in an endless series of bomb attacks and other outrages, many of them directed at public gatherings or holy places.
Shia religious leaders tried to restrain their followers from carrying out acts of revenge, and were largely successful in the opening phases of the insurgency.
But over the past year, revenge killings against Sunnis have been multiplying.
The destruction of the Shia shrine at Samarra on 22 February gave the country a powerful shove towards the gaping precipice.
"The country is slipping gradually into a very dangerous and serious situation," said senior Shia politician Hussein Shahrastani in a BBC interview.
"After the attack on the shrines in Samarra, it became very clear that the insurgents and terrorists are determined to drag the country into civil confrontation and civil war.
Insurgents have attacked some of Shia Islam's most important shrines
"Religious and political leaders have been prudent enough to control the masses from a violent backlash, but nobody can be sure [what will happen] if the terrorist attacks continue in this fashion."
Since Samarra, hundreds of people have fled their homes in areas where they feel uncomfortable or threatened, with Sunnis moving out of mainly-Shia neighbourhoods and vice versa.
The movement has not become a stampede, but has worried the authorities.
"So far, we have received 350 families, of between three and 12 members each," said an official of the office run by the militant Shia cleric Moqtada Sadr in the heavily-Shia stronghold of Sadr City in Baghdad.
"We are trying to settle them in schools and public centres here and in other Shia areas."
The Sadr group has agreed to set up a joint committee with the Sunni Association of Muslim Scholars to try to deal with the situation.
A spokesman for the association said that at least 60 Sunni families fled the Nahrawan area east of Baghdad after being threatened in the wake of sectarian killings there last week.
Prime Minister Ibrahim al-Jaafari said on Tuesday that displaced families would be returned to their homes under the protection of Iraqi police or army forces.
The Iraqi army said that 13 families who had fled to the Shia district of al-Sholeh had been taken home under protection. The Association of Muslim Scholars said that 25 Sunni families had moved out of al-Sholeh itself.
The US ambassador in Baghdad, Zalmay Khalilzad, interviewed by the Los Angeles Times, said that "the potential is there" for sectarian violence to become full-blown civil war in Iraq.
While he believed the country had pulled back from the brink, "if another incident [occurs], Iraq is really vulnerable to it at this time, in my judgment."
"We have opened the Pandora's box and the question is, what is the way forward?" Mr Khalilzad said.
"The way forward, in my view, is an effort to build bridges across communities."
He warned of a drastic scenario if Islamic extremists were able to use part of a fragmented Iraq as a base for regional expansion - it would make Afghanistan under the Taleban look like "child's play", he said.
His grim assessment contrasted with more upbeat comments from the Chairman of the Joint Chiefs of Staff, Gen Peter Pace, who said on Sunday that things in Iraq were going "very, very well, from everything you look at".
Sectarian tension has been a catalyst for violence in Iraq
Ambassador Khalilzad said the formation of an Iraqi national unity government would provide a major obstacle to those trying to push the country towards civil war.
But nearly three months on from the 15 December elections, the formation of any kind of government is still a distant prospect.
There is a deadlock over who should take the most powerful post of prime minister, with the Shia nomination of the incumbent Ibrahim al-Jaafari strongly rejected by the Kurdish, Sunni and secular factions, whose co-operation is necessary to the formation of a coalition government.
Once that problem is solved, haggling over both the political programme and the personnel in a national unity government is expected to take weeks, if not months.