Three female suicide bombers, thought to be aged between 11 and 15, struck on Friday morning, an official with the National Emergency Management Agency told BBC Hausa.
It follows bomb attacks on a mosque on Thursday, which killed at least 32.
Maiduguri is often targeted by the Islamist militant group Boko Haram.
No group has yet said it was behind the attack during Thursday’s evening prayers, that also left many people injured.
More than 100 people were killed in three explosions last month in the city, which is considered the birthplace of Boko Haram.
In Thursday’s attack, officials say the first suicide bomber blew himself up inside the mosque, with a second bomber detonating explosives as people rushed to help those injured in the initial blast.
The explosions caused parts of the mosque to collapse, leading to further injuries.
Nigerian military spokesman Sani Kukasheka Usman told the BBC’s Newsday programme that Boko Haram was resorting to suicide attacks because “they have been degraded to the extent that they can no longer fight collectively”.
This year the security forces have reclaimed most of the territory previously captured by the group in north-eastern Nigeria.
Two million people have been forced from their homes since the militants launched their insurgency in 2009.
Nigerian President Muhammadu Buhari made combating the group a key campaign pledge as he sought election this year, but attacks by the Islamist group have intensified since he came to power.
Mr Usman said the Nigerian army was still determined to meet a deadline set by President Buhari to defeat Boko Haram by the end of the year.