Nigeria religious riots kill at least 52 KADUNA, Nigeria (Reuters) - At least 52 people were killed in religious rioting sparked by three suicide bombings against churches in northern Nigeria, where the dead were piled up on Monday in mortuaries and cemeteries in the city of Kaduna. Rioting broke out on Sunday after suicide car bombers attacked three churches in northern Nigeria, killing at least 19 people and wounding dozens. Christian youths had set up roadblocks and dragged Muslims from cars or motorbikes and killed them, witnesses said. Although there has been no immediate claim of responsibility for Sunday's church bombings, Islamist sect Boko Haram, which is waging an insurgency in the northeast against President Goodluck Jonathan's government, had claimed deadly church attacks on the previous two Sundays, as well as others. A Reuters reporter visited two hospitals in Kaduna. At the St Gerald Hospital, spokesman Sunday Aliyu said there were 40 bodies in the hospital morgue and 72 people being treated for burns and other wounds. At Barau Dikko Hospital, Matron Hassana Garba confirmed 12 dead and two injured people being treated. On Monday evening residents reported gunfire and explosions in Damaturu, the capital of northeast Yobe state and the site of several previous attacks by Boko Haram. We are all indoors, the explosions and gunshots have been going on since 5pm. It's boom, boom, boom, everywhere," Oluchi Jonah, a local resident, told Reuters by phone. Local police were not available for comment. In November, 65 people were killed in attacks claimed by Boko Haram on churches, mosques and police stations in Damaturu, where security forces often clash with Islamists in gun battles. Corpses littered church grounds in parts of Kaduna on Monday. They were piled one on top of the other in an old cemetery, some charred. A soldier guarding the site said there were at least 30 bodies of people killed in the violence there. They had been dragged to the secluded cemetery, in a majority Christian neighborhood, by the mobs, he said. We've had violence before, but this is the worst I've seen," he said. The violence stoked fears of wider sectarian conflict in Nigeria, an OPEC member and Africa's top oil producer that is home to the world's largest equal mix of Christians and Muslims. He hid in a bush when rampaging Christian youths pulled Muslims off their motorcycles and beat them to death. If they saw me, that would be it," the second-hand clothes seller said, estimating 15 people were killed right by where he was hiding. Boko Haram church bombings seem calculated to trigger wider sectarian strife, often striking at the heart of Nigeria's volatile "Middle Belt," where the mostly Christian south and Muslim north meet. The Islamists' leader, Abubakar Shekau, has said the attacks on Christians were in revenge for the killings of Muslims. But such attacks have usually failed to spark sustained conflict in a nation whose Muslims and Christians mostly co-exist peacefully, despite periodic flare-ups of sectarian violence since independence from Britain in 1960. Additional reporting by Tim Cocks in Lagos, Mike Oboh and Joe Brock in Abuja and Ibrahim Mshelizza in Maiduguri; Editing by Louise Ireland