A local official says at least seven people have been killed in an explosion targeting a taxi in northeastern Nigeria's largest city.

Bello Dambatta, an emergency response official, says six people were killed at the scene of Wednesday's attack and another died at a hospital. He says at least four people were injured.

It is unclear if a bomb had been planted on the taxi or if a passenger detonated explosives after boarding. The explosion occurred as the taxi approached a gas station.

Northeastern Nigeria is the epicenter of Boko Haram's seven-year uprising that has claimed more than 20,000 lives.

Maiduguri city had been spared deadly bombings in recent months as soldiers were able to shoot suicide attackers before they reached their targets.