The Emir of Gwoza, Idrissa Timta, was shot dead in the Tashan Alade area of Borno state while travelling by road to the funeral of another senior cleric, Borno's government said.
The Emir of Uba, Ali Ibn Ismaila Mamza, and the Emir of Askira, Abdullahi Ibn Muhammadu Askirama, were also in the convoy but were not harmed.
"The gunmen... Specifically targeted the vehicle conveying the three emirs and opened fire," said a statement from Borno's state secretary, Baba Ahmed Jidda.
The Islamist rebels, who have killed thousands in a five-year uprising, have repeatedly targeted Nigeria's Islamic monarchs, whom they accuse of betraying the faith by submitting to the authority of the secular government.
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