Explosions and gunfire have been heard in the northern Nigerian city of Gombe, witnesses say.
Reports said the blasts happened around the time of evening prayers, quickly followed by gunfire.
Witnesses said people were fleeing an area of the city near a prison and police station. It is not clear if there are casualties.
Earlier on Friday, gunmen killed five people at a mosque in Kano, the main city in northern Nigeria, police said.
A police spokesman said the attackers arrived on motorcycles and opened fire at worshippers.
Nigeria is experiencing a surge in ethnic and sectarian violence.
Gombe has previously been targeted by the Islamist sect Boko Haram. In January, an attack on a church in the city left six worshippers dead.
There were few details of the latest attack. Gombe state police commissioner Orubebe Ghandi Ebikeme described the situation as “very bad” but gave no further comment.
Boko Haram, whose name means “Western education is forbidden” in the local Hausa language, is fighting to create an Islamic state and wants to impose Sharia law across Nigeria.
The group has been responsible of a series of deadly attacks and assassinations across northern Nigeria in the past 17 months.
Source: BBC News