A university in Nigeria's northern city of Kano has been rocked by gunfire and an explosion, which may have targeted Christian students.

An army spokesman said a number of people had been wounded and were being rushed to hospital, but it was not clear how many casualties there were.

Staff at Bayero University told the BBC that the incident was still going on.

Reports said the explosion appeared to target a lecture theatre where Christian students hold services.

Military spokesman Lt Iweha Ikedichi told the Associated Press news agency: "There were casualties, but I don't have exact figures. Some have been rushed to local hospitals."

He said soldiers and police had surrounded the university and were searching for the gunmen.

No group has said it launched the attack, but the Islamist militant Boko Haram group is active in Kano.

Boko Haram carried out a bombing in Kano in January that killed about 150 people, its deadliest attack to date.

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.

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