Scores of people are feared to have been killed and wounded in a bomb blast at a mosque in Nigeria, military officials said.
The blast occurred at the main mosque in the city of Kano, Nigeria's second-largest city, where 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 under way with the injured and dead being taken away from the scene.
Immediately after the blasts, hundreds of angry youths took to the streets, throwing stones, brandishing sticks and shouting at security officials.
The palace of the Emir of Kano is near the central mosque. Palace officials said the Emir, one of the highest ranking Islamic figures in Nigeria, is out of the country.
Police did not immediately provide a precise death toll.
The militant group Boko Haram has carried out numerous such attacks in northern Nigeria and Kano has been repeatedly hit.
In September, two suicide bombers killed at least 15 students at a government college. In July, five suicide bombings were carried out over the course of a week. More than 1,500 have been killed this year in the insurgency.
Meanwhile, a police anti-bomb squad defused six bombs planted near a mosque and a market in Maiduguri, according to Borno state police spokesman Gideon Jubrin.
Fears are running high in Maiduguri after two female suicide bombers detonated explosives on Tuesday at a commercial centre. At least 70 people were killed.