MAIDUGURI, Nigeria (AP) — The governor of Nigeria's northeast Yobe state is ordering all schools closed to avoid attacks by Islamic militants who have killed dozens of students and teachers.

The U.N. children's agency, meanwhile, said Monday that 48 students and seven teachers have been slain since June in northeast Nigeria.

"There can be no justification for the deliberate targeting of children and those looking after them," said UNICEF regional director Manuel Fontaine.

Gov. Ibrahim Gaidam issued the order after visiting students with burn and gunshot wounds from Saturday's attack on a boarding school outside Potiskum, the state's second largest town. Extremists set a dormitory ablaze, burning some students alive. At least 29 students and one teacher were killed.

Last month Islamic fighters attacked at least two schools, killing 16 students and two teachers.

Gaidam said such attacks could be averted if the military would resume cell phone service cut to three northeastern states since the government declared a state of emergency May 14. He said residents could have alerted the military by cell phone.

Authorities have blamed the spate of recent attacks on Boko Haram, a terrorist group whose name means "Western education is sacrilege." The group and its offshoots have killed more than 1,600 civilians in a series of suicide bombings and other attacks since 2010, according to an Associated Press count.

The group's stronghold is Maiduguri, the capital of neighboring Borno state, which is 230 kilometers (about 145 miles) from Yobe. It is also believed to have a strong network in Adamawa state, prompting President Goodluck Jonathan to deploy thousands of troops to regain control of the region.

The ongoing violence has become the biggest security threat in years to Africa's biggest oil producer and has drawn criticism of President Jonathan's administration, who many Nigerians believe did not respond quickly to the growing threat of terrorism in the country.

Soldiers say they have killed and arrested hundreds of fighters. But the crackdown, including attacks with fighter jets and helicopter gunships on militant camps, appears to have driven the extremists into rocky mountains with caves, and shifted their focus to schools and markets.

Recent attacks by suspected Boko Haram militants aimed at schools or school officials in the region indicate a strategic target on unsuspecting students and school officials who are unable to fight back.

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Makurdi reported from Johannesburg. Associated Press writer Michelle Faul in Lagos, Nigeria contributed to this report.

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  • A female student stands in a burnt classroom at Maiduguri Experimental School, a private nursery, primary and secondary school burnt by the Islamist group Boko Haram to keep children away from school in Maiduguri, northeastern Nigeria, May 12, 2012.(PIUS UTOMI EKPEI/AFP/GettyImages)

  • In a Sunday, Dec. 25, 2011 file photo, onlookers gather around a car destroyed in a blast next to St. Theresa Catholic Church in Madalla, Nigeria after an explosion ripped through a Catholic church during Christmas Mass near Nigeria's capital Sunday, killing scores of people, officials said. A radical Muslim sect, Boko Haram, claimed the attack and another bombing near a church in the restive city of Jos. (AP Photo/Sunday Aghaeze, File)

  • In a Sunday, Dec. 25, 2011 file photo, medical officials try to treat a victim of a bomb blast at a Catholic church near Nigeria's capital at Suleja General Hospital in Suleja, Nigeria. An explosion ripped through a Catholic church during Christmas Mass near Nigeria's capital Sunday, killing at least 25 people, officials said. A radical Muslim sect, Boko Haram, claimed the attack and another bombing near a church in the restive city of Jos. (AP Photo/Dele Jones, File)

  • This file image made available from Wednesday, Jan. 10, 2012, taken from video posted by Boko Haram sympathizers shows the leader of the radical Islamist sect Imam Abubakar Shekau. (AP Photo, File)

  • Bodies of people alleged to have been killed in a Friday attack on a town hall meeting of the Christian Igbo ethnic group lie on the floor in a hospital morgue in Mubi, in the Adamawa state of northern Nigeria, Saturday, Jan. 7, 2012. The town hall attack, which left at least 20 dead, is one of a string of deadly attacks claimed by radical Muslim sect Boko Haram. (AP Photo)

  • An anti bomb police officer collect soft drink can bombs recovered from islamic militants in Kano, Nigeria, on Tuesday, Jan. 24, 2012. Police said Tuesday that members of the radical Islamist group Boko Haram dressed in uniforms resembling those of soldiers and police officers when they launched their attack Friday in Kano. (AP Photo/Sunday Alamba)

  • In this Monday, Oct. 8, 2012 photo taken with a mobile phone, a police officer walks past a burnt out shopping mall in Maiduguri, Nigeria. (AP Photo/Abdulkareem Haruna)

  • In this frame grab from TV footage shot by the Nigeria television authority on Monday, Oct. 8, 2012 but aired Tuesday, Oct. 9, 2012, shows people lying down (condition of people unknown) on a street in Maiduguri, Nigeria. (AP Photo / Nigeria Television Authority)

  • A partially burnt down communication tower destroyed by Boko Haram in Maiduguri, Nigeria, Friday, Sept. 7, 2012. A radical Islamist sect claimed responsibility Friday for attacks on mobile phone towers which have crippled communications in Nigeria's northeast, as security forces struggling to control the violence said they had gunned down seven suspected sect members. (AP Photo/Haruna Umar)

  • Weapons and ammunition along with police uniforms and bulletproof vests recovered from suspected Boko Haram sect members, put on display in Bukavu Barracks in Kano, Nigeria, Wednesday, March. 21, 2012. (AP Photos/Salisu Rabiu)

  • Burnt our cars are seeing at the business and skills center following gun battle and explosions by the Boko Haram sect, in Potiskum, Nigeria, Saturday, Oct. 20, 2012. (AP/Photo Adamu Adamu)

  • Burnt out school block following a gun battle and explosions by the Boko Haram sect in Potiskum, Nigeria, Saturday, Oct. 20 , 2012. (AP Photo/Adamu Adamu)

  • In this Wednesday, March 21, 2012 file photo, suspected members of the radical Islamist sect Boko Haram, are detained by the military, in Bukavu Barracks in Kano state, Nigeria after an attack on a police headquarters, the home of a senior police officer and setting fire to a nearby bank. (AP Photos/Salisu Rabiu-file)