A female suicide bomber blew herself up in a college in Kano on Wednesday, killing six people and critically wounding another six in the fourth such attack by a woman in Kano in less than a week, a security source said.
The bomber targeted youths who were looking at a notice board for National Youth Service in Kano Polytechnic, the source said.
There was no immediate claim of responsibility, although militant group Boko Haram, which is fighting for an Islamic state in Nigeria, has repeatedly bombed Kano as it radiates attacks outwards from its northeast heartlands.