A military official in Nigeria says scores of people are feared to have been killed and wounded in a bomb blast at a mosque.

Capt. Ikechukwu Eze said the Friday blast occurred at the main mosque in the city of Kano, Nigeria's second-largest city. Hundreds had gathered to listen to a sermon from the chief imam of Kano.

Witnesses say heavy smoke could be seen billowing in the sky from a long distance away.

Rescue operations are underway at the bomb site, with the injured and dead being taken away from the scene.