Kano - Four people, including a mother and her two children, were killed on Monday when a vehicle hit a mine planted by Boko Haram islamists near the town of Banki on the Nigerian border with Cameroon, sources told AFP.The vehicle was part of a convoy heading to Maiduguri under military escort when it hit the mine as the insurgents opened fire a "few kilometres" from the border town of Banki, they said."The explosion killed four people including a mother and her two children while nine people were severely injured," a militia assisting the military in fighting Boko Haram in Banki told AFP."The injured were taken to a Unicef-run health facility in Banki where they are receiving treatment," he said.The explosion was preceded by a barrage of gunfire on the convoy from Boko Haram fighters lurking at the side of the highway, said a driver in the convoy who gave his first name as Abdullahi.Escorting troops returned fire and repelled the attack "but one of the vehicles hit a mine the attackers planted," the driver added."The vehicle exploded. Four people inside were killed and nine were injured."Banki, which is 130km southeast of the Borno state capital Maiduguri, has been repeatedly targeted by Boko Haram suicide attacks. In August, 11 people were killed when the jihadists raided a camp housing 45 000 displaced by the insurgency and stole food supplies.