Whether the work of shadowy Islamic extremists from outside the region or local agitants, a deadly bombing on Indonesia's Sulawesi will unravel months of painstaking effort to reconcile warring Christians and Muslims on the island, community leaders say.
Two bombs exploded minutes apart in a busy market place in the predominantly Christian town of Tentena, early Saturday killing 20 people and leaving more than 50 injured.
Although officials say the attack could be the work of Islamic militants blamed for other major atrocities in Indonesia, it has threatened to reignite sectarian tensions that have previously resulted in widespread bloodshed.
Efforts to reign in conflict in the region, where more than 1,000 died in a year of fighting before a 2001 peace deal, have had patchy success, with sporadic violence continuing to claim lives.
But senior negotiators say the latest incident, the worst single attack in the region, has dealt a crippling blow to the fragile peace effort.
"With this incident we will have to start from scratch again," said Reynaldi Damaniq, who as the head of the Central Sulawesi Christian church, has been at the forefront of the peace efforts.
Damaniq in January this year set up with his Muslim counterpart Adnan Nazar the Humanitarian Alliance, a group of 40 representatives from both religions working to mend fences between the two communities.
"We have now to convince the people that this is not a matter of religion but of certain individuals, regardless of their faith, who do not want to see peace in this world," Damaniq told AFP.
Decades of violence in Sulawesi culminating in the brutal conflict of 2000 have seen thousands of people from both religions flee their homes and seek refuge from persecution and harassment.
While more than 85 percent of Indonesia's 214 million people are Muslims practicing a moderate and tolerant brand of the religion, Sulawesi's population is equally divided between Christianity and Islam.
Tensions between the two groups began emerging in the 1960s under a controversial transmigration policy which encouraged Muslims from the densely-populated main island of Java to fan out across the archipelago.
Many indigenous and Christian communities in Sulawesi and other parts of the country, including the troubled eastern Maluku island chain, felt their interests were being sidelined by Jakarta in its effort to reshape the nation. Tensions reached boiling point during the downfall of dictator Suharto in 1998, when the effects of the Asian financial crisis in Indonesia saw violence break out, much of it targeting ethnic Chinese and Christian communities.
In Sulawesi, open conflict broke out in 2000 and resulted in the deaths of more than 1,000 people before a tentative peace deal was struck.
Until Saturday, the Christian enclave of Tentena had been one of the few places in Sulawesi's Poso district where Muslims could live in peace with their Christian neighbours.
On May 23, Christians and Muslims both took part in a ceremony to mark the Islamic prophet Mohammed's birthday at the town's main mosque. "But now, things have certainly changed. The old animosity is back," Damaniq said.
Anger at the blast has stoked resentment towards the government and security forces, widely perceived as doing little to prevent the violence. Police reinforcements at the scene of the blast were greeted with jeers on Sunday.
"We are dissatisfied with the government and the police because whenever the victims are Christians, they are not serious in investigating the cases," said an emotional resident, housewife Rosalino Tamanyo, a 41-year-old homemaker. "What is happening is an outburst of accumulated disappointment among the population," Tamanyo said.
Damaniq said the priority of community leaders was primarily to ensure the perpetrators of the bombing were brought to justice, unhindered by sectarian differences. "Confidence building can only be tackled at a later stage," he said.
Both sides have been swift in their attempts to limit the damage. A delegation of Muslim leaders arrived from Poso on Sunday to meet their Christian counterparts to discuss how to lessen tensions. The Muslims have also sent ambulances, doctors, and medicines.
"It will not be an easy challenge to face but we are ready to take the chance, peace is imperative, we have been living in violence for too long," Damaniq added.