Borno state police chief Mohammed Abubakar said Monday that gunmen shot a nurse dead and wounded four others who were playing poker at a bus stop in the city of Maiduguri.
Police say the same group of gunmen killed a security officer in a separate attack hours later.
Police suspect members of a radical Muslim sect known as Boko Haram.
The group, whose name means “Western education is sacrilege” in the local Hausa language, is responsible for a string of targeted killings over the last year in Maiduguri.
The group has recently expanded its reach. A man claiming to speak for the group told a local paper and the BBC that it orchestrated a suicide bomb in Nigeria’s capital last week.