Scores Left Dead As Explosion Rocks Secondary School In Potiskum.

At least 13 people have been killed after an explosion ripped through a secondary school in Potiskum as students gathered for morning assembly before classes began.

A teacher at the school, a medic and a rescue worker said on Monday that blast happened at the Government Comprehensive Senior Science Secondary School in Potiskum, Yobe state.

The rescue worker told AFP news agency that 13 bodies had been taken to hospital with more than 30 others left "with various degrees of injuries". 

"The students had gathered for the morning assembly when something exploded in their midst with a thunderous sound at exactly 7:50am local time (0650 GMT)," added a teacher, who asked not to be identified.

"The explosion has affected many students but I can't say how many because we are now evacuating the victims to the hospital which is just 100 metres away," the teacher said.

A medic at the Potiskum General Hospital, where the victims were taken, said scores of students had been admitted.

"We are still receiving casualties from the school which is a stone's throw from here," the medic said.

"Our priority now is to save the injured, so we have not started a headcount of the victims."

The latest violence came days after a suicide bomber killed at least seven people outside a commercial bank in the northeast town of Azare on Friday.