Hundreds of people have been fleeing areas of north-eastern Nigeria, after a 24-hour wave of violence apparently targeting Christian communities.At least 29 people have died in four attacks in Adamawa state, prompting the state governor to impose a curfew.The Islamist Boko Haram group has said it carried out several attacks.One Boko Haram faction has warned all southerners - who are mostly Christian and animist - to leave the mainly Muslim north of Nigeria.Last week President Goodluck Jonathan declared a state of emergency in Yobe and Borno states, as well as Plateau state in central Nigeria and Niger state in the west, following a surge in ethnic and sectarian violence.Adamawa, which borders Borno state where Boko Haram emerged, was not included.More than 500 people have been killed by the group over the past year.President Jonathan, who is a Christian, has vowed to crack down on the group but Christian groups have accused him of not doing enough to protect them.Pastor Ayo Oritsejafor, president of the Christian Association of Nigeria, said his members would protect themselves against the attacks."We have decided to work out means to defend ourselves against these senseless killings," he said, quoted by the Associated Press news agency.The pattern of the killings suggested "systematic ethnic and religious cleansing", he added.Shoot-outAt least 17 people were killed in Mubi, in Adamawa, as gunmen opened fire in a town hall where members of the Christian Igbo group were meeting.They had been meeting to organise how to transport the body of an Igbo man who was shot dead by gunmen on motorbikes on Thursday evening."It was while they were holding the meeting that gunmen came and opened fire on them," a resident said.More attacks on a church and hairdressing salon in Adamawa's capital, Yola, left more than 10 dead.The attacks prompted state governor Murtala Nyako to impose a 24-hour curfew.Security was tightened and troops were seen patrolling the streets.A resident in Yola says all shops and businesses are closed and only essential services are being allowed through the deserted town.Meanwhile people fled the streets of the town of Potiskum, in Yobe state, after an attack on banks and the police headquarters followed by a shoot-out between gunmen and security forces."We are afraid the soldiers will raid and burn our homes like they do in Maiduguri each time Boko Haram attack," local resident Amiru Umar told AFP.The Islamist Boko Haram group said it had carried out the attacks in Mubi and Yola, and another in Gombe on Thursday night in which at least six people died.The group has staged numerous attacks in northern and central areas in recent months - on Christmas Day it attacked a church near the capital, Abuja, killing dozens of people.Meanwhile, the government is also facing the bleak prospect of a general strike in two days' time amid popular fury over its removal of a fuel subsidy which has seen fuel prices double for ordinary Nigerians.Boko Haram, whose name means 'Western education is forbidden', is fighting to overthrow the government and create an Islamic state.