A sudden volley of violence in Northern Ireland has pitched the province and its protracted peace process back into deep uncertainty, with serious questions resurfacing about the compatibility of two communities at loggerheads for a generation.
As an uneasy calm returned to the streets of Belfast following the worst violence for more than a decade, analysts, politicians and locals predicted that the three nights of rioting posed a serious threat to the process of reconciliation that has been slowly building in Northern Ireland since 1994.
The unrest, triggered by a decision to reroute a traditional Protestant march away from Catholic areas, has seen large crowds of Protestants attacking police and British army units, torching cars and setting up improvised roadblocks across the city, to vent their anger at a political process that they feel marginalizes them.
At least 60 people have been injured since Saturday, and 63 people have been arrested.
"Trouble has been brewing, but I don't think most people expected this," says Adrian Guelke, professor of comparative politics at Queen's University in Belfast. "The pessimistic view is that this is an indication of just how deep the antagonisms are and how impossible it will be to get agreement."
The rioting marks a sudden deterioration in the situation following fitful progress in recent years toward a settlement for Northern Ireland's feuding communities, republican Catholics who favor a united Ireland, and Protestant unionists who favor preserving ties with Britain.
Optimism soared in July with an IRA statement renouncing the armed struggle it has waged for 35 years in a civil conflict that left more than 3,000 dead.
But paradoxically, the breakthrough may have aggravated tensions by leaving Protestants with the impression that the IRA and the republican movement has made political gains through carrying out terrorism, while the Protestant Unionists have been stripped of their traditional power and influence in Northern Ireland.
"The peace process is meant to be a negotiation - a two-way thing," says Paul Hannah, a bartender from one West Belfast community where rioters used a hijacked bus to barricade a small suburban road before setting fire to it.
"Instead, the Protestants have to make all the concessions and we don't even get a say in what happens."
Cathal McCall, a professor at Queen's University, says that in the deprived areas caught up in the violence there was a sense "that the working-class Catholics have benefited from the peace process far more than working class Loyalists."
Dr. McCall notes a second current of tension coursing through the communities affected by the rioting. The fact that the police, traditionally Protestant, have been striving to recruit Protestants and Catholics in equal numbers to make the force more representative, has alienated some hard-line Protestants, who no longer see the forces as "their own."
Moreover, a police crackdown on vigilante acts by Protestant paramilitaries has incensed groupings like the Ulster Volunteer Force (UVF).
"The loyalist group, the UVF, are feeling a bit piqued at the police force for making arrests for their feud with their own splinter group, the LVF," he says.
"The police aren't the most popular people right now," says John Adair, owner of a Belfast news agents located near the burned-out bus barricade.
"At the moment, they police don't come down here unless they have to - that's why the bus was set on fire - so that the police would have to respond and come down here. And when they did, some of the lads were waiting and had a crack at them."
The violence has caught the British government in a difficult position. It is hoping that Protestant anger will be assuaged when the IRA is actually seen to be destroying weapons.
"The hope is that when this happens, Unionists will wake up and see that the threat really is gone and take a more balanced view," says Dr. Guelke.
Until then, the government has to decide whether to declare that formal cease-fires which Protestant paramilitaries have by and large observed since 1994 have effectively been broken.
Some politicians in Belfast are incensed that the government still clings to the "pretense" of a cease-fire despite evidence of live bullets being fired at police.
Other experts warn however that things will get worse if the Protestant cease-fire is declared dead.
"In the short term this could provoke a reaction from the UVF," says McCall. "At the same time, the IRA are about to announce further weapons decommissioning. The reaction of Unionist politicians to this will be critical."
Although the violence has mostly taken place far from the city center and away from tourist sites, the renewed violence also deals a serious blow to Northern Ireland's economy and its fledgling tourism industry.
"The violence is only going on in a tiny area but it has such a huge impact," says Lisa McMurray, Director of Communications at Belfast's Visitor and Convention Bureau.
"Tourism is becoming much more important. Before 1994 Belfast had around 200,000 visitors a year; in 2004 it was 5.9 million," says Ms. McMurray.
"Yesterday we had the millionth visitor to our Welcome Centre [for tourists] and we held a little celebration but it was totally overshadowed."
• Mark Rice-Oxley contributed to this report from London.