MAIDUGURI, Nigeria — Nigerian troops Sunday repelled Islamic extremists who attacked from four fronts on Maiduguri, the biggest city in northeast Nigeria, with several civilians killed by aerial bombs and grenades and mortar shells on the ground.

Soldiers said hundreds of insurgents died.

Terrified residents fled homes shaking from five hours of heavy artillery fire and streamed in from the outskirts of the besieged city of 2 million, already crowded with another 200,000 refugees from the fighting.

In a separate attack, a suspected Boko Haram suicide bomber killed himself and eight others Sunday at the home of politician Sabo Garbu in Potiskum, in neighboring Yobe state, according to witness Abdullahi Mohammed.

Garbu is contesting a legislative seat in Feb. 14 balloting that includes a presidential election too close to call. Boko Haram denounces democracy.