At least 31 people have been killed in a double bombing in the Nigerian city of Jos, while a 13-year-old girl in an explosives vest was arrested in the northern city of Kano. The blasts in Jos happened on Thursday at a makeshift market near the Terminus bus station, which had been set up after a twin car bomb attack in May killed at least 118 people. Mohammed Abdulsalam, coordinator for the National Emergency Management Agency in the city, said the scene of the attack was a densely populated area. "The bodies recovered so far are 31 but rescue workers are at the scene and the figures may change," added Pam Ayuba, spokesman for the Plateau state governor Jonah Jang. The city, which is the capital of Plateau, lies in Nigeria's "Middle Belt" where the mainly Muslim north meets the mostly Christian south. It has been targeted by Boko Haram Islamists in the past but is also a hotbed of ethnic and sectarian tensions that frequently boil over into deadly violence. In Kano, a senior security source and a nurse said a 13-year-old was arrested on Wednesday after she and a male accomplice walked into a clinic seeking medical treatment. Clinic staff were on alert because of a double suicide attack by two women on a textile market 20km away, just hours earlier. "We alerted the police who immediately mobilised and arrested the duo," said one nurse, who asked to remain anonymous for security reasons. "On searching her, the police discovered explosives hidden under her hijab, confirming our suspicion. They took her and the man accompanying her away." The senior security source said the young girl was from the northeastern state of Bauchi and had been part of the "suicide team" that attacked the busy Kantin Kwari textile bazaar. Four people were killed in that attack and seven others injured. "Her arrest is a huge breakthrough in unravelling the spate of suicide attacks by young girls in the city," the source added. Boko Haram has increasingly used women as suicide bombers in attacks ranging from Borno state in the far northeast to Niger to the northwest.