Gunmen believed to be Nigeria's Boko Haram Islamic extremists attacked a convoy of motorists along a recently secured highway, killing at least seven people and injuring many others, including soldiers in a military escort, witnesses said.

The Maiduguri-Biu highway has been one of the most dangerous routes in northeastern Nigeria for three years because of Boko Haram attacks. The Nigeria military recaptured it last year and declared it safe, but the military escorts motorists moving in convoy along the road.

Eyewitness, Dauda Pambe, said he was among the travelers guarded by soldiers when gunmen launched the ambush attack on Saturday.

"We were somewhere between Bulabulin and Dogonwaya villages when the Boko Haram gunmen opened fire on the vehicles ahead of us in the convoy," said Pambe. "The first vehicle was hit on the tire and the driver could not proceed so the passengers alighted and fled into the bush. The second vehicle was a pickup van carrying many passengers, and many of them could not escape."

The gun fight continued for some time with many passengers ducking in their vehicles to avoid being hit by bullets, said Pambe.

The incident came three days after Boko Haram gunmen suffered a heavy loss of members after a foiled attempt to attack a military base in Borno state. In that incident, a large number of the insurgents stormed a military base in Kamaya but failed to dislodge the soldiers.

Neither the police nor the military has yet issued a statement on the Maiduguri-Biu road attack.

AP