Eight people were killed on Monday when a female suicide bomber detonated her explosives at a mosque in northeast Nigeria, in the latest attack in the restive region.
The head of the Borno state emergency management agency, Ahmed Satomi, said the blast happened at about 5:30 am (0430 GMT) in the London Ciki area of Maiduguri, which has been at the epicentre of Boko Haram violence since 2009.
"She killed eight people and injured 15 others. The mosque was being guarded by civilian JTF (joint task force militia) during prayers," he told AFP.
"Unknown to them, the girl was being pursued from another part of town by residents who were suspicious of her movement at the time.
"When she approached the mosque, they demanded that she stop to be searched but she suddenly bolted into the mosque and set off her bombs."
Three other female suicide bombers were located in Maiduguri at about the same time, said Satomi.
Two were killed in the Mammanti area as they tried to cross the ditch around the city perimeter while another set off her explosives in the suburb of Simari, he added.
Borno state police commissioner Damian Chukwu said the first two were killed shortly before midnight while the third was intercepted shortly after.
It is the second time in a week that four female suicide bombers have sought to cause carnage in Maiduguri.
Last Monday, at least 19 people were killed and 23 others injured when four women set off their bombs in the Molai Kolemari area of the city.
Boko Haram has increasingly used women and young girls as human bombs as they have been forced out of captured territory due to a sustained military counter-insurgency.
Maiduguri has been repeatedly attacked in recent months, with mosques, markets, camps for those displaced by the conflict and other civilian "soft" targets hit regularly.
Boko Haram meanwhile released a video online showing 10 women who they claimed to have kidnapped last month during an attack on a convoy.
On June 20, the jihadists ambushed a convoy of vehicles under police escort heading towards the town of Damboa on a highway outside Maiduguri.
Initially local news reports said that 16 policewomen had been abducted in the ambush. But police officials denied the reports, insisting only a policeman was killed in the attack.
In the five-minute video, 10 women of varying ages sit on the ground in an undisclosed bush location surrounded by lush vegetation.
"On behalf of all of us... I plead with the Nigerian government to intervene so that we are freed the way the Chibok schoolgirls were freed," said one of the hostages, who gave her name as Amina Adam Gombiya.
Gombiya said she was a teacher at the Federal College of Freshwater Fisheries in the town of Baga on the shores of Lake Chad.
In May, Nigeria secured the release of 82 schoolgirls abducted by Boko Haram from the remote town of Chibok in a prisoner swap deal.
The militants seized 276 schoolgirls from the town in Borno state in April 2014, triggering global condemnation and drawing attention to the bloody insurgency.
Fifty-seven escaped in the immediate aftermath. Of the 219 who did not manage to flee, 106 have either been released or found, leaving 113 still missing.
Thousands of civilians have been abducted since the insurgency began in 2009. The jihadists use women and young girls as sex slaves and suicide bombers, while men and boys are recruited as fighters.