Gunmen have attacked a teacher training college in the Nigerian city of Kano, with officials saying at least 15 people have been killed.
The attackers exchanged fire with police outside the college before running inside.
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.
Officials said two suicide bombers also died in the attack.
"We heard several shots from the gate area and after a few minutes we heard an explosion at the [lecture] theatre," lecturer Sanusi Umar told Reuters.
"The attackers were wearing suits and were running and shooting everywhere," he added.
President Goodluck Jonathan condemned what he termed a "dastardly attack".
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, Mr 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 2,000 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.
Who are Boko Haram?
- Founded in 2002
- Initially focused on opposing Western education - Boko Haram means "Western education is forbidden" in the Hausa language
- Launched military operations in 2009 to create Islamic state
- Thousands killed, mostly in north-eastern Nigeria but also in attacks on police and UN headquarters in capital, Abuja
- Some three million people affected
- Declared terrorist group by US in 2013