Gunmen have attacked a teacher training college in the Nigerian city of Kano, with officials saying at least 13 people have been killed.
Students were seen fleeing from the city's Federal College of Education and at least one explosion was heard.
Another 34 people were injured.
It is not clear who was responsible, although suspicion will fall on militant Islamist group Boko Haram, which has been waging an insurgency in Nigeria since 2009.
One student told the BBC by phone he had seen 17 dead bodies at the scene.
In July, the city suffered a spate of five attacks in four days, one of which also targeted a college and killed six people.
In May 2013, Nigeria's President Goodluck Jonathan imposed a state of emergency in the northern states of Borno, Yobe and Adamawa, vowing to crush the insurgency.
However the militants have stepped up attacks, killing more than 2000 civilians this year, according to New York-based Human Rights Watch.
Boko Haram's name translates as "Western education is forbidden", and it has carried out several attacks on schools and colleges, seeing them as a symbol of Western culture.
In April, it raided a boarding school in Chibok town in the northern state of Borno, and is holding more than 200 girls that its gunmen abducted during that attack.