ABUJA, Nigeria — The death toll from a shooting at a mosque in northwestern Nigeria has risen to 50, a local official said Wednesday. Gunmen stormed the mosque in the town of Unguwan Mantau, in Katsina state, during morning prayers on Tuesday, according to lawmaker Aminu Ibrahim.

Criminal gangs, locally called “bandits,” have for years preyed on rural communities in Nigeria’s northwest and centre. What began as disputes between herders and farmers over land and water has escal