Many are feared dead in a car bomb explosion in the North-eastern Nigerian city of Maiduguri.
Blood-spattered people were seen fleeing and vehicles crashed into each other, while soldiers fired automatic weapons.
A suicide bomber is suspected of being behind the blast, reportedly near a market.
The Islamist militant group, Boko Haram, has carried out numerous attacks in the region.
Its campaign of violence is aimed at imposing Islamic rule in northern Nigeria.
The Director of Defence Information, Maj. Gen Chris Olukolade, confirmed the bomb blast incident in Maiduguri when our correspondent contacted him on the telephone.
Olukolade said that security operatives had arrested a suspected insurgent in relation with the explosion.
He said that the suspect was already assisting the investigating team with useful information.
Olukolade said that investigation into the latest violence was ongoing adding that details of the incident would be made known later.
An eyewitness said he had seen what appeared to be dead bodies on the ground, and another spoke of seven fatalities.
A second car is reported to have been set on fire by the blast.
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