GUNMEN killed five Nigerian police officers and two civilians during an attack in the southeastern Imo state on, a police spokesperson said, the latest incident in a state riven by gang and separatist violence. Armed groups have attacked police stations and government and electoral offices in states in the southeast, which the government often blames on the banned separatist Indigenous People of Biafra (IPOB) group. IPOB denies the charges. Imo police state spokesperson Henry Okoye confirmed the death of the officers and civilians but did not give details. Africa's most populous nation, Nigeria, is prone to widespread insecurity, with gun…