An explosion on Sunday rocked an area near a theatre at a university in the Nigerian city of Kano used by Christian students for services, a security source and residents said.
"There was a huge explosion at the open air theatre close to the entrance of the old site of the university during a church service by Christian students," the source said. Residents also reported hearing gunfire.
Details were not yet clear, including whether there were casualties.
Islamist group Boko Haram claimed on January 20 attacks in Kano, the largest city in Nigeria's mainly Muslim north, when coordinated bombings and shootings left at least 185 dead, the extremists' deadliest attack yet.
On Thursday, bomb attacks at newspaper offices in the capital Abuja and the northern city of Kaduna left at least nine people dead.