Boko Haram Islamist militants have attacked the north-east Nigerian city of Gombe, residents say.
Fighters overran a checkpoint on the edge of the city and explosions and gunfire could be heard, witnesses added.
Nigerian troops backed by a fighter jet were said to be trying to drive the militants back.
Nigeria has postponed elections due to be held on Saturday amid concerns over the insurgency in the north-east.
Gombe - capital of Gombe State - has previously suffered suicide attacks but correspondents say this is the first time Boko Haram has launched a direct assault on the city.
Reports said militants first attacked the town of Dadin Kowa, about 40km (25 miles) from Gombe.
Ground troops with air support then battled to keep the insurgents from entering the city.
The BBC's Abullahi Kaura in Abuja says residents have fled into the bush and into nearby hills.