A high-ranking traditional leader has been killed in northern Nigeria after his convoy came under attack by suspected Boko Haram militants.
Gunmen shot dead the Emir of Gwoza, Shehu Mustapha Idris Timta, in his car.
Boko Haram has waged an increasingly bloody insurgency since 2009 to create an Islamic state in Nigeria.
Nigeria's President Goodluck Jonathan vowed to wage "total war" against the group, which has been held more than 200 girls captive since last month.
"They shot the emir of Gwoza. He died on the spot," Wali Ibrahim, an aide to the emir, told the BBC Hausa service.
"After he died we reversed back from that area and we went to the army checkpoint," he added.
Two other emirs, who were also in the convoy that was attacked in north-eastern Borno state, escaped unhurt.
They were all on their way to the funeral of the emir of Gombe, who died recently in London.
Borno state government confirmed the attack and said the gunmen were believed to be Boko Haram members, Reuters news agency reports.
BBC Nigeria analyst Naziru Mikailu says traditional rulers have been targeted for assassination by Boko Haram before, but attacks on them are rare.
Emirs, who command a lot of respect in the north, have taken a stand against the militants, he says.
In January 2013, suspected Boko Haram fighters attacked the convoy of the emir of Kano, one of the country's prominent religious leaders, as he returned from a mosque to his palace in Kano city.
Mr Jonathan declared a state of emergency in May 2013, deploying more troops to the three northern states where Boko Haram is most active - Borno, Adamawa and Yobe.
Boko Haram retaliated by stepping up its bombing campaign in cities and launching mass attacks on small towns and villages.
Correspondents says since the kidnapping of the schoolgirls from their school in Chibok, the attacks have become an almost daily occurrence.
A resident of Koma in Adamawa state told the BBC that at least 17 people were killed in an attack on his village near the border with Cameroon on Thursday morning.
Earlier this week, the BBC learned that the government called off a deal to swap some of the girls for Boko Haram fighters in custody.
The US, UK, China and France are among those countries to have sent teams of experts and equipment to help to locate the girls
Nigeria under attack
- 20 May: Twin bomb attacks killed at least 122 people in the central city of Jos
- 18 May: Suicide blast on a busy street in northern city of Kano kills four, including a 12-year-old girl
- 5 May: Boko Haram militants slaughter more than 300 residents in the town of Gamboru Ngala
- 2 May: Car bomb claims at least 19 lives in the Nigerian capital, Abuja
- 14 April: Twin bomb attack claimed by Boko Haram kills more than 70 at an Abuja bus station; the same day, the group abducts more than 200 schoolgirls from the remote northern town of Chibok