Jos, Nigeria (CNN) -- An Islamic militant group in northern Nigeria has claimed responsibility for attacks that killed at least 25 people in a rash of violence against the country's minority Christians, officials said, after it issued an earlier ultimatum that gave Christians three days to leave the area.





Gunmen opened fire on residents Friday, killing at least 15 people who were mourning the deaths of two slain businessmen, said Rev. Paul Alhamdu, chairman of the Christian Association of Nigeria.





At least eight people were also killed on Thursday in a church shooting in northeastern Nigeria, a pastor at the church said, as sectarian violence spirals and the country is shaken by angry protests over fuel subsidies.





Gunmen attacked the Deeper Life church in Gombe, the capital of Gombe state, Thursday evening as worshipers held a prayer meeting, according to the Venerable Joseph Ninyo, a pastor with the Anglican Diocese of Gombe.





He said at least 20 people were being treated at a hospital, one of whom is in intensive care.





"Many tried to run but were gunned down," eyewitness Konson Danladi said. "I was just outside the church when the men came and started shooting, and I ran."





Police said the militant group Boko Haram claimed responsibility for both attacks, but CNN could not immediately confirm the claims.





The church targeted in Gombe is attended predominantly by Ibo Christians from southern Nigeria.





Boko Haram has been blamed for months of widespread bloodshed in Nigeria, with churches and police stations among the targets.





The group also claimed responsibility for a series of attacks on churches on Christmas Day.





The rising tide of violence led Nigerian President Goodluck Jonathan to declare a partial state of emergency in four northern states, in a bid to contain Boko Haram, whose name means "Western education is a sin."





The latest sectarian attack comes as Nigeria also faces a nationwide wave of popular protests over the removal of a gas subsidy that had kept prices artificially low.





What is behind Nigeria fuel protests?





Union leaders have called for a national strike beginning Monday if the government does not reverse the decision, which resulted in the cost of a liter of gasoline more than doubling virtually overnight.





Furious Nigerians have already taken to the streets this week, staging "Occupy Nigeria" protests and mass demonstrations across the country, and there have been calls from some quarters for the president to be impeached.





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Nigeria, an oil-rich nation of about 167 million people, is regularly voted among the most corrupt countries in the world, and citizens complain that the money saved by ending the fuel subsidy is highly likely to be siphoned off by a few and salted away into offshore accounts.





The government has said the money will be used to fund infrastructure projects, such as building refineries so Nigeria can produce its own gasoline rather than having to import it.





Tires burn, protesters flood Lagos





Elizabeth Donnelly, with the Africa Programme at London-based think tank Chatham House, told CNN the two issues together -- the sectarian violence and the fuel subsidy protests -- present the biggest challenge yet for Jonathan, who was elected president last year after taking the reins in 2010 when the former president died.





Although the government struck a blow against Boko Haram in 2009 with the capture of its leader, Mohammed Yusuf, it has since become more of a "franchise," or umbrella organization, for the actions of individual groups, making it harder to manage the problem, Donnelly said.





Protesters make demands known





"We can trace these sorts of attacks to issues of underdevelopment, poverty, lack of resources and so on. The fact that it's framed in religious language is worrying," she said, particularly given the sectarian violence that has broken out in Nigeria in recent years.





The country's leadership needs to rise above politics and use the kind of language that will bridge the growing gap between different parts of Nigerian society, she said, rather than just treating the problem as a security issue.





But the challenge of restoring calm will be compounded by
Who has been blamed? who was responsible for the attack? Gunmen attacked what church as worshipers met for service? Who attacked the church? Who has been blamed for other attacks on churches? Where is the Deeper Life church? What did an eyewitness describe that they saw? what did the eyewitness describe? What was the group called?
Boko Haram An Islamic militant group in northern Nigeria Deeper Life Gunmen Boko Haram Gombe, "Many tried to run but were gunned down," "Many tried to run but were gunned down," Boko Haram
question: Who has been blamed?, answer: Boko Haram | question: who was responsible for the attack?, answer: An Islamic militant group in northern Nigeria | question: Gunmen attacked what church as worshipers met for service?, answer: Deeper Life | question: Who attacked the church?, answer: Gunmen | question: Who has been blamed for other attacks on churches?, answer: Boko Haram | question: Where is the Deeper Life church?, answer: Gombe, | question: What did an eyewitness describe that they saw?, answer: "Many tried to run but were gunned down," | question: what did the eyewitness describe?, answer: "Many tried to run but were gunned down," | question: What was the group called?, answer: Boko Haram