A suicide bomber has killed five people at a mosque in the north-eastern Nigerian city of Maiduguri, security officials say. The attack, reportedly by a teenage boy, narrowly missed one of Nigeria's most revered Muslim traditional leaders, the Shehu of Borno. The blast happened at a mosque near his palace in the centre of the city as Friday prayers finished. Maiduguri is the stronghold of the militant Islamist group Boko Haram. BBC Nigeria analyst Jimeh Saleh says the group has not targeted a mosque before, but it is known to have assassinated Muslim leaders. "A lone suicide bomber blew himself up while targeting some dignitaries coming back from the Friday prayer," Bala Hassan, Borno state's police commissioner, told the AFP news agency. Deputy state governor Zanna Umar Mustapha said he was standing next to Shehu Umar Garbai el-Kanemi when the bomb went off. "It was God that saved me and the Shehu, otherwise we would have been dead by now," he told AFP, adding that the religious leader's clothes were splattered with blood. Just over a year ago, Boko Haram claimed responsibility for assassinating the Shehu's younger brother in Maiduguri. At the time a sect spokesman said traditional institutions would come in for attack for colluding with the authorities. Boko Haram, which means "Western education is forbidden" in the Hausa language, seeks to overthrow Nigeria's government and establish an Islamic state. The group adheres to a strain of Islam that outlaws any kind of activity linked to Western culture. Its militants have stepped up attacks in the last year, targeting the UN headquarters in the capital, Abuja, churches and security buildings. The subsequent military crackdown in northern Nigeria has failed to improve the security situation and some argue it has also prompted the Islamist militants to increase the number of attacks. Earlier this week, the group said it killed two politicians in Jos who were attending a funeral for people killed in communal violence in Plateau state, which lies on the fault line between Nigeria's mainly Muslim north and Christian and animist south. Boko Haram first came to prominence in 2009 when hundreds of its followers were killed when they attacked police stations in Maiduguri. The next year the group started to stage drive-by shootings on government targets in revenge for the death of their founder in police custody.