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.
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. ---AFP