A peace conference is taking place in the central Nigerian state of Plateau, the scene of fierce ethno-religious fighting earlier this year.
The clashes in May between Christians and Muslim left dozens dead and drove some 250,000 from their homes.
Representatives of all the communities are to discuss conflicts over land and religion at the month-long conference.
President Olusegun Obasanjo, who on Wednesday visited Yelwa, where the fighting began, opened the meeting.
The clashes in Plateau sparked more fighting in the northern city of Kano and raised communal tensions across Nigeria, which has similar numbers of Muslims and Christians and hundreds of different ethnic groups.
More than 10,000 people have been killed in communal clashes since Mr Obasanjo was elected in 1999, ending years of military rule.
Justice sought
The BBC's Elizabeth Blunt in Yelwa says the town is still a sorry sight, with whole streets where every house has been destroyed.
Most of the people who fled were Muslims, but everyone suffered - Christian churches were burnt out, as well as the town's old mud-built mosque.
The president told his audience that he had come to celebrate peace, but said he had to see peace before he could celebrate it.
He said the day he had been forced to impose emergency rule, exactly three months ago, had been one of the worst of his life.
But the violence had started to spread and no responsible government could have failed to act.
He praised the work of the emergency administrator in restoring peace.
Mostly the crowd listened quietly, but raised a cheer when the president promised them help to rebuild their homes.
But standing where the president could not miss them were a group of children with posters accusing the suspended state governor of having failed to prevent the violence, and saying that the killers should be brought to justice.