The attack hit Bayero University in northern Nigerian city of Kano when Christian students were holding a Sunday worship in the lecture theatre. Security sources said the bombing was followed by shootings in the lecture theatre.
According to media reports, at least six people were killed in the attack, which came months after 180 people had died in Kano when Islamic fundamentalist sect, Boko Haram, targeted the residents.
A bomb squad and military units were searching for the gunmen who mounted the attack at Bayero University.
The attack took place in one of the lecture theatres used as a place of worship by Christians," army spokesman Lt Iweha Ikedichi was quoted as saying by BBC. "There were casualties, but I don't have exact figures. Some have been rushed to local hospitals." Eyewitnesses said the toll was likely to be high but not yet ascertainable.
Boko Haram sect had recently bombed houses of newspaper companies in Nigeria, including the influential 'Thisday', killing eight people. The sect says it has an avowed mission of turning the country into an Islamic state with Sharia rule.
But some analysts think there are political motives behind its attacks which also targeted a United Nations building last year. Nigeria has a population of 180 million, evenly divided among Christians and Muslims, with the former mostly found in the South while the latter in the North.