Prosecutors in Chad had suggested 44 prisoners killed themselves, but a new report says otherwise.Read more
Africa editor, BBC World Service
Suspected Islamist Boko Haram militants have killed 15 sleeping people and wounded six others in a grenade attack in northern Cameroon, reports say.
A security source and a local official told the Reuters news agency that the attackers targeted a camp for displaced people in the village of Nguetchewe, close to the border with Nigeria.
The victims - including women and children - were asleep when the assailants arrived.
Boko Haram has been fighting in north-east Nigeria for over a decade but has also been active in Cameroon, Chad and Niger. A regional military operation has failed to stop the attacks.
Donkey cart attack
Meanwhile, in northern Burkina Faso at least six people, most of them children, have been killed after a donkey cart ran over an improvised explosive device (IED) in a region which has seen many jihadist attacks.
A security source told a French news agency that four other people were injured and had been taken to a hospital in the nearby Ouahigouya town.
The victims were returning from grazing with their animals.
Since 2015 Burkina Faso has seen an upsurge in Islamist violence – spreading from Mali - and more than 1,000 people have been killed and a million have fled their homes.
Africa editor, BBC World Service
Nigeria's President Muhammadu Buhari has said the security forces could do much better in their efforts to keep the country safe.
In a rare interview, Mr Buhari described the situation in northern and central regions as "very, very disturbing".
"I believe the military, the police and other law enforcement agencies, from the reports I am getting, I think they could do much better," he is quoted by the AFP news agency as saying.
Mr Buhari came to power five years ago promising to defeat Boko Haram Islamists in the north-east, but the insurgency continues.
Ethnic and criminal violence, including kidnappings and cattle raids, is intensifying in the north-west and central regions.
Last week, the senate passed a resolution calling for military chiefs to resign or be sacked over the deteriorating security situation.
It's not yet known who is behind the series of explosions in Nigeria's north-eastern city of Maiduguri that left at least three people dead and six injured on Thursday.
Bello Danbatta, the head of security for Borno state's Emergency Management Agency, said that four rocket-propelled explosives were fired from outside the city, landing on separate sites.
Nigerian security expert Bulama Bukarti said if these were used it indicates a worrying sophistication in the group's capacity.
He added that the Islamist militant group unsuccessfully attempted to launch explosives into the city on the eve of the presidential elections in February last year.
The security situation in Nigeria's north-east remains challenging - earlier this week Borno's governor came under attack in Baga town, after visiting one of the military's "super camp" bases.
These bases are part of the army's strategy to defeat Boko Haram and are meant to be better protected than smaller outposts. But critics say the military's withdrawal to these camps has ceded territory to the jihadist groups, and that the army has continued to come under attack.
Last month Boko Haram released a video in which a fighter claimed to be a part of a branch of the militant Islamist group in Niger state - it is the largest state in Nigeria, which borders the capital Abuja and is further south than their usual area of operation.
A presence outside of Nigeria’s north-east would be a concerning development.
Nigeria's north-eastern city of Maiduguri, in Borno state, has been hit by a number of explosions, according to eyewitnesses.
Emergency services say three people have died and six injured. Residents in the city had been preparing for Muslim holiday celebrations of Eid al-Adha.
The explosions are reported to have taken place inside the city early Thursday evening.
The head of security for Borno state’s Emergency Management Agency, Bello Danbatta, said that four rocket-propelled grenades were fired from outside the city, landing on separate sites.
Eyewitness Mohamed Abubakar told the BBC that the explosions took place in a busy part of the city, when traders and residents were heading home.
In recent years, areas outside Maiduguri have been attacked by Islamist militants from the Boko Haram group, but it is unusual for an attack to strike inside the city.
The Islamic State group has claimed responsibility for the killing of four aid workers and a security guard in Nigeria's north-eastern Borno state.
UN Secretary General Antonio Guterres has called on the Nigerian authorities to bring the perpetrators to justice.
A photograph, published by the Islamic State's newspaper, shows five men wearing civilian clothing sitting on the ground, blindfolded.
Standing behind them are five other armed men wearing military clothing, with their faces covered.
The image appears to be a screen grab from a propaganda video. The Islamic State in West Africa Province, Iswap, is a splinter group of the Islamist extremist group Boko Haram.
The aid workers were kidnapped last month and their deaths confirmed earlier this week.
It underlines the risks humanitarian workers face in north-eastern Nigeria.
The region has seen more than a decade of violence from Boko Haram that has forced more than two million people from their homes and killed more than 30,000.
The United Nations has condemned the killing of five aid workers by militants in Nigeria.
The militants abducted the five men in the north-eastern Borno state in June. Nigeria’s President Muhammadu Buhari has blamed the Islamist militant group Boko Haram for their deaths.
UN humanitarian coordinator in Nigeria, Edward Kallon, said "it is unacceptable that those who are trying to help are being attacked and killed".
"This incident will not deter the international community from providing aid to millions of Nigerians who desperately need assistance in the north-east," he said in a statement.
He also expressed concern at the number of checkpoints set up by armed groups along main supply routes.
"These checkpoints disrupt the delivery of life-saving assistance and heighten the risks for civilians of being abducted, killed or injured, with aid workers increasingly being singled out," he said.
The five aid workers were employees of humanitarian agencies Action against Hunger and International Rescue Committee.
The Islamist Boko Haram group has been carrying out bombings, assassinations and abductions in Nigerians since 2009.
BBC News, Abuja
Parliamentarians in Nigeria have called for the military bosses to resign following persistent killings by armed gangs and Islamist militants in the north of the country.
A resolution adopted by Nigeria's senate has called for the chief of defence staff, as well as air force, army and naval chiefs to resign.
Responding to the resolution, President Muhammadu Buhari insisted that the appointment of military chiefs is a presidential prerogative and added that, in his capacity as Commander-in-Chief of the Armed Forces, he will do what is in the best interest of the country.
In the past, similar calls for the sacking of the country's security chief have not been heeded by the president.
Reports say more than 350 Nigerian soldiers will formally leave the army due to a loss of confidence in leadership and low morale.
In the past the Nigerian military has suspended approvals for voluntary retirement requests from soldiers, with some accused of cowardice and sabotage when criticising military leadership.
Nigeria has been engaged in an ongoing conflict against the Islamist militant group Boko Haram for more than a decade.
The campaign of terror has left more than 30,000 people dead and displaced more than two million people.
To find out more about the background of Boko Haram watch this: