JOS, Nigeria (AP) — Violence across central and north Nigeria killed 21 people, as gunmen attacked both security forces and civilians in a region where ethnic and religious tensions still simmer, officials said Wednesday.

The majority of the killings happened in Plateau state, where rioting and violence between Christians and Muslims of different ethnic groups have killed hundreds in recent years. Gunmen killed 14 people belonging to a Christian ethnic group in the region in the Riyom local government area, said Mark Lipdo, who runs a Christian advocacy group called the Stefanos Foundation. The dead included three children and their mother, Lipdo said.