The attack in the Maiduguri killed both the girls and one other person and left another 18 injured.
Boko Haram are believed to be behind the attack but have not claimed responsibility.
The group is known for using women and girls to carry out suicide attacks and similar tactics have been used elsewhere.
In Libya a female suicide bomber used three children as a decoy in a attack that killed four soldiers and injured another 12.
‘They got out of a rickshaw and walked right in front of me without showing the slightest sign of emotion,’ he said.
‘I tried to speak with one of them, in Hausa and in English, but she didn’t answer. I thought they were looking for their mother,’ he added.
At least 20,000 people have been killed and more than 2.5 million displaced by the unrest caused by Boko Haram.