Soldiers and civilian fighters said they held off a siege by hundreds of Boko Haram militants who launched an attack on a heavily fortified army base in northeastern Nigeria’s biggest city.

The assault is evidence of the Islamist insurgency’s remaining strength even as it loses territory. Militants, including female suicide bombers, rode motor scooters and Toyota pickup trucks into Maiduguri late Wednesday, firing artillery that residents said shook the city.

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