Gunmen have stormed three schools in Nigeria and kidnapped more than 50 children, teachers and local residents have said. The armed abduction happened in Mussa, Borno state in north-eastern Nigeria on Friday morning. Witnesses said security forces were unable to open fire because the suspects used the children as human shields while fleeing on motorbikes. Most of the missing children are aged between two and five years old. They were taken from the town's Government Day Secondary School, Mussa