Red Cross officials say at least 16 people have been killed in a gun and bomb attack at Bayero University in Nigeria’s northern city of Kano.
Six others were in a serious condition following the attack at Bayero University campus where Christian worshippers were holding a service.
Nigerian police are searching for the gunmen.
No group has said it launched the attack, but the violent Islamist Boko Haram group is active in Kano. It has recently attacked churches.
Nigeria’s central government has struggled to contain the militant group, which operates mainly in the predominantly Muslim north, but has also struck as far south as the capital, Abuja.
Sunday’s attack took place in one of the lecture theatres used as a place of worship by Christians.
A witness told AFP news agency the attackers had first thrown in explosives and fired shots, “causing a stampede among worshippers”.
“They now pursued them, shooting them with guns. They also attacked another service at the sporting complex.”
Another witness spoke of “pandemonium”, and said he had seen two men shooting indiscriminately.
Mohammed Suleiman, a history lecturer at the university, said security guards had to run for their lives when the violence broke out.
“For over 30 minutes a series of bomb explosions and gun shots took over the old campus, around the academic blocks,” he told Reuters news agency.
A Red Cross spokesman said adults – possibly professors – and three women were among the casualties. Several needed urgent blood transfusions.
Kano state police spokesman Ibrahim Idris said that by the time police arrived, the attackers had “disappeared into the neighborhood”. A manhunt is under way.
But the situation at the university was now calm, according to the Red Cross spokesman.
Boko Haram carried out a bombing in Kano in January that killed more than 180 people, its deadliest attack to date.
• 2002: Founded in Maiduguri
• July 2009: Hundreds of members killed when Maiduguri police stations stormed; police capture and kill sect leader Mohammed Yusuf
• Dec 2010: Bombed Jos, killing 80 people; blamed for New Year’s Eve attack on Abuja barracks
• Jun-Aug 2011: Bomb attacks on Abuja police HQ and UN building
• Dec 2011: Multiple bomb attacks on Christmas Day kill dozens
• Jan 2012: Wave of violence across north-east Nigeria; Kano bombing kills at least 180