Officials say four security officers and at least four assailants have died in two northern Nigerian cities which have seen a spate of sectarian violence. Kano state police chief Ibrahim Idris said policemen killed four men who were attempting to bomb a mosque Sunday in the major city of Kano. Air Commodore Sani Ahmed, a Nigerian air force official in Kano, said motorcycle-mounted gunmen also killed two air force officers Sunday. The violence follows a Friday night clash in the northeastern city of Damaturu that left a policeman and a soldier dead. Yobe state police spokesman Toyin Gbadagesin said police blamed members of Boko Haram sect for the Damaturu attack. He said security officers then razed a house believed to be harboring sect members.