Many of the black-clad women in mourning who marched the dusty streets of Jos this week carried messages of peace.

Some called for justice for those murdered, others for an end to the violence that has shattered the city and set the whole of Nigeria on edge. But one woman had a different message. Her banner read: "God hears when we cry. Be warned." Her warning was being heeded yesterday in a city now strictly segregated between Muslims and Christians.

A dusk-to-dawn curfew is manned by hundreds of police and soldiers, who have carved up the city with impromptu barricades. Some neighbourhoods have their own people keeping watch. Sporadic gunshots have been heard most nights since the massacre. Almost a week has passed but there is no single truth about what actually happened in Jos; about who has died and how many have died; and about how the city, once known for tourism, has become a byword for sectarian slaughter.

One of the truths can be found in the mass graves at Dogo Nahawa, a village of mud bricks and corrugated iron roofs a few miles south of the city. Most of the bodies from the latest massacre lie under a fresh mound of red earth still criss-crossed with the tracks of the bulldozer that dug the pit. The grave is unmarked but Peam Shut knows where it is. Seventeen members of his family are among the more than 100 bodies that lie there.

He approaches, clutching his face and crying, to say what happened. He was woken last Sunday morning by a gunshot. He went outside to see a group of men, carrying machetes and clubs, throw a petrol bomb at his brother's house. He watched as his brother's wife, Hanatu, tried to flee: "She couldn't get away, they rushed her and they butchered her." The attackers then turned his way and shouted: "There are the other cattle." That's when Peam ran. Somehow he was able to hide but his wife and son were not so lucky, and were cut to pieces.

A short distance away, across a furrowed patch of maize, is the village itself. This was the killing field where hundreds of Muslims from the Fulani people set upon their erstwhile neighbours, the mainly Christian Berom. Bloodstains have dried on the wall of an outlying house, and next to it a blackened tree marks the spot where Dung Gwonm was hacked and burnt to death.

A few metres further away are the ruins of Pastor Johana Gyang Jugu's church. His loss is drawn in deep lines on his hollow face. He tells what has become a familiar story of waking to gunfire and desperately running for your life. His wife, Rose, and 18-year-old daughter, Mary, ran with him but were separated in the confusion. He turned back to see them both cut down. "I tried my best," he said, as if to apologise. "There is nothing I can do, I am just crying."

Dogo Nahawa ought to be a ghost town. Fire has consumed many houses, thick smoke has painted their walls black, roofs have collapsed into rooms. In one small house, a metal door has been wrenched aside, releasing a burnt food odour where bags of maize and beans have been roasted next to somebody's charred motorcycle. But survivors have returned, anxious to make sure the raiders don't come back to take over the village permanently.

Amidst the burnt-out cars, five-year-old Benet is queuing for food. The little boy can't speak but others explain that he has been orphaned, his mother and father killed in the slaughter. Yesterday, a local Christian group came to see him and take him into care. No-one knows for sure how many orphans there are or how many have died here and in the other three villages attacked on the same night.

Mark Lipdo, who works for the evangelical Christian organisation the Stefanos Foundation, was among the first to reach the villages after the violence. He says that at least 370 people are buried at Dogo Nahawa. Others say that 100 bodies lie in the mass grave. The state governor's office have said that at least 500 people were killed but the Red Cross puts the toll closer to 200.

Sadly, in Jos these numbers matter. For Mr Lipdo, the villagers are the face of a "new Darfur" – victims of a "violent Muslim expansion". He is among those who see this as part of a world-wide Islamic advance. But this is only his truth. Jos is the capital of Nigeria's fertile "middle belt", a highland plateau where missionaries converted animist farmers to Christianity. Tin deposits were later found in the area and the colonial government brought Hausa Muslim labourers from further north. Jos and its satellite villages have been mixed and metropolitan ever since.

It is – as the local police commissioner Ikechukwu Aduba says – "a mini Nigeria". Like Jos, Africa's most populous nation is thought to be evenly split between the two faiths, with Muslims predominant in the north and Christians in the south, but everywhere a mixed picture. In Jos, population growth and economic decline has increased competition for land and other resources, heightening tension between communities.

Politics here have been poisoned by the distinction between the longer-standing Christians, or "indigenes", and Muslim "settlers". The former are favoured in land rights, the latter denied the opportunity to stand in elections. This has caused resentment, which has erupted in 2001, 2004 and 2008, leaving thousands dead, many more displaced and the city polarised. The truth depends on where you are in Jos.

Another truth is lying on a bed on the second floor of a small clinic called La Tahzan in the Muslim north of Jos. Two-year-old Hassan Harouna has to lie on his front. The skin from his lower back over his buttocks and down his left leg has been burned away. He and his mother were doused in petrol and set alight in an attack by Christians on Muslims in January. His burns are shaped the way they are because he was tied to his mother's back.

His father Abdullahi explains: "They invaded our settlement at Kuru Karama and started to burn the houses. Then they herded us into one place and started chopping with machetes." Abdullahi escaped with three of his children, believing his wife and Hassan had died. Hassan lay among the dead – many of whom were stuffed into wells that were later sealed as mass graves – for 24 hours before he was found. His mother, Ranatu, is in a hospital across town. She is not expected to survive.

Like everything else in Jos the circumstances of January's mass-killings are disputed. Some in the Christian community insist that Muslim youths launched an unprovoked attack at a church. Others say it was the rumours that a new building was intended for use as a mosque that sparked the clashes. Text-message rumours and inflammatory statements by officials prompted a mob to attack the Fulani Muslim settlement at Kuru Karama. Estimates of the numbers killed in clashes that began on 17 January run as high as 326.

The attacks of last Sunday are believed to be in reprisal for the January killings. Some 200 people have been arrested this week, 49 of them Fulanis of whom several have confessed to taking part in the latest massacre. There is widespread mistrust of the authorities' handling of both bouts of killing. Muslim anger is focused on the governor Jonah Jang, who in turn has fallen out with local army chief, Major General Saleh Maina. "The truth about Jos is that we have a competition for political control," says Solomon Selcap Dalung, a lecturer in international law at Jos University. "Instead of consolidating peace and reaching out to the aggrieved, the state government has been sowing disharmony. It is like Rwanda, where the machinery of government is used to divide people. The truth is that it is not about religion – it is politics and while it continues peace will remain a stranger in Jos."

Muslims went to Friday prayers yesterday. Sani Mudi, a community leader at the central mosque in Jos, was appealing for calm. He described accusations of al-Qa'ida involvement in the region as "nonsense" and the fear of Islamisation as "unfounded and irresponsible."

The cycle of violence in the area "is creating an atmosphere of hatred," he said. "What we have in Jos is extensive poverty which is driving people mad. And we have reckless politicians. For the poor and uneducated there is nothing to hold on to apart from religious slogans you can shout."

As he is speaking, his office inside the mosque has the appearance of an emergency room with community leaders rushing in and out for hurried conversations. There is little optimism that further violence can be avoided and much sadness for what has been lost. In a final lament, he says: "I attended a mixed school with both Christians and Muslims, but my children cannot do that. It is not possible now."

Roots of conflict: Jos attacks

*What happened in Jos?

At least 200 people in the mainly Christian villages south of Jos were killed last Sunday. The attacks have been blamed on Fulani muslims and are seen as a reprisal for January violence in which most of the victims were Muslims.

*Why is this happening?

Christians and Muslims used to live peacefully in the central Plateau state. But Muslims who have lived there for decades are still classed as settlers, and in the last decade there have been regular bouts of sectarian killing. The underlying reasons are economic – with competition for resources – and political – with a struggle for domination.

*Could the violence spread?

Yes. Sectarian violence in Nigeria has spread before. And the crisis also mirrors a north-south power struggle in the government. The ruling party generally observes a gentleman's agreement to rotate power between north and south, but the replacement of the critically ill President Umaru Yar'Adua, a northerner, with Goodluck Jonathan, a southerner, has upset that balance.

*What's at stake?