Nigerian security forces say they have killed at least eight militants in fighting in the north-eastern city of Maiduguri.

The army said the members of Islamist militant group Boko Haram died in an exchange of gunfire, and that troops had safely detonated three bombs.

Three civilians were also injured, said the army, although witnesses reported seeing at least 20 corpses at a market.

Boko Haram has launched a series of deadly attacks across northern Nigeria.

"The JTF (military) has killed eight Boko Haram members this afternoon who attacked and wounded three civilians at the Baga Road market," Lt Col Hassan Mohammed told Reuters by telephone.

"The sect members were engaged... in a shoot-out."

Boko Haram, whose name means "Western education is forbidden", wants to establish Islamic law in Nigeria.

Last week the group said it had carried out an attack on a prison in central Kogi state, freeing seven of its members.