More than 130 members of the Boko Haram terrorist group have surrendered to Nigeria's military.
Mohammed Bashir, a man who had posed as the group’s leader Abubakar Shekau in numerous videos, was also been killed in clashes, the military said on Wednesday.
Defence spokesman Major-General Chris Olukolade said: “In the course of those encounters, one Mohammed Bashir, who has been acting or posing on videos as the deceased Abubakar Shekau ... known as leader of the group, died.”
Following the surrender, Nigeria's military has released photographs of dozens of detainees sitting on the floor and the alleged body of the leader.
Over the past five years, the group has killed thousands of people in guerrilla attacks on military installations and against civilians. In the past two months, its ambitions have grown as it has started to seize and hold ground in Nigeria.
After members of the extremist group seized several small towns and declared the area an Isis-style ‘Islamic Caliphate’, Nigeria’s army stepped up its military operations in the rural northeast.
The Nigerian army said that 135 Boko Haram fighters had handed their weapons to troops on Tuesday in the town of Biu, near the epicentre of Boko Haram’s campaign to carve out an extremist Islamist state.
Reports from BBC News citing the country’s military claimed the number was as high as 260, as a further 133 members reportedly surrendered in north-eastern Nigeria.
Last August, Nigeria's military said Shekau may have died of gunshot wounds some weeks after a clash with soldiers.
Following the reports, the man appearing in Boko Haram videos appeared to look different, with a rounder, less narrow face and a wider nose.
In pictures: Nigeria kidnapped schoolgirls
In pictures: Nigeria kidnapped schoolgirls
A total of 276 girls were abducted from the northeastern town of Chibok, in Borno state, which has a sizeable Christian community. Some 223 are still missing
One of the kidnapped girls looks into a camera
One of the missing girls talking to the camera
The missing Nigerian schoolgirls, wearing the full-length hijab and praying in an undisclosed rural location. Boko Haram alleging they had converted them to Islam
Girls wearing the full-length hijab holding a flag reading "There is no god, but Allah" and "Mohammed is Allah's prophet"
A man claiming to be the leader of Nigerian Islamist extremist group Boko Haram Abubakar Shekau
Abubakar Shekau speaks on the video
Girls, wearing the full-length hijab and praying are filmed by an unidentified man (R) in an undisclosed rural location
People carry signs as they attend a protest demanding the release of abducted secondary school girls in the remote village of Chibok in Lagos
A protester demonstrates against the kidnapping of school girls in Nigeria, outside the Nigerian Embassy in London
Chief International Correspondent Christiane Amanpour and Prime Minister David Cameron appearing on the BBC1 current affairs programme
People participate in a "Bring Back Our Girls" campaign demonstration and candlelight vigil in Los Angeles
Girls holding heart shaped banners in a "Bring Back Our Girls" campaign demonstration and candlelight vigil in Los Angeles
14/19 South Africa
South Africans protest in solidarity against the abduction of hundreds of schoolgirls in Nigeria by the Muslim extremist group Boko Haram and what protesters said was the failure of the Nigerian government and international community to rescue them, during a march to the Nigerian Consulate in Johannesburg
Karilyn Coates (10) joins others in a candlelight vigil for the more than 300 girls abducted by Boko Haram in Nigeria, at All Souls Unitarian Church in Colorado Springs
Mothers of the missing Chibok school girls abducted by Boko Haram Islamists gather to receive informations from officials. Nigeria's president said that Boko Haram's mass abduction of more than 200 schoolgirls would mark a turning point in the battle against the Islamists, as world powers joined the search to rescue the hostages
Former Nigerian Education Minister and Vice-President of the World Bank's Africa division (3rd L) Obiageli Ezekwesilieze speaks as she leads a march of Nigeria women and mothers of the kidnapped girls of Chibok, calling for their freedom in Abuja
18/19 Bring Back Our Girls
Kelly Hoppen tweeted: 'Please make sure you do this, we must stand together and not forget them'
19/19 Bring Back Our Girls
E.L. Rock Star tweeted: 'Join The Movement'
As the group has transformed from a radical but relatively peaceful clerical movement to an insurrection, Shekau had appeared in a number of videos issuing threats and taunting the authorities.
In one such clip, he claimed responsibility for the abduction of 200 schoolgirls from the remote village of Chibok in April, which sparked an international outcry and the '#BringBackOurGirls' social media campaign. The majority remain in captivity.
The surrender comes after one of the more than 200 schoolgirls abducted was freed this week, according to police and a parent of some of the other missing girls.
She is receiving medical attention after she was found running in a village, having spent four days in the bush, said a parent, who has two girls still with the insurgents and who declined to be named.
Additional reporting by Reuters