The video posted on Twitter shows one of the alleged victims pleading for authorities to release detained militants so the girls can be freed.
The girl, who is wearing a headscarf, has been identified as one of the 276 students abducted from a remote school in north-eastern Nigeria in April 2014.
She claims that some of her kidnapped classmates died in aerial bombardments by the Nigerian military. She also said that 40 have been “married” to Islamic extremist fighters.
The video, posted by Nigerian journalist Ahmad Salkida and cited by SITE Intelligence Group, also shows a fighter warning in the Hausa language that if President Muhammadu Buhari’s government battles Boko Haram with firepower, the girls will not be seen again.
“Presently, some of the girls are crippled, some are terribly sick and some of them, as I had said, died during bombardment by the Nigerian military,” the fighter says, appearing before a group of more than 40 young women in headscarves and hijabs.
“If our members in detention are not freed, let the government and parents of the Chibok girls know that they will never find these girls again.”
It says the Chibok girls are held by Boko Haram leader Abubakar Shekau, who is in a leadership battle with a lieutenant named by the Islamic State group as the new leader of what it calls its West Africa Province.
Dozens of the schoolgirls kidnapped from Chibok in April 2014 escaped on their own within two days of the abduction. One girl escaped this year, saying she had been led to freedom by her Boko Haram “husband”.
Some 218 remain missing in the abduction that shocked the world.
In the video, the fighter says the Nigerian government has repeatedly lied to its citizens with promises to quickly free those kidnapped from Chibok Government Girls School, who now are all over 18 years old.
The young woman in the video begs for help to free them.
“Oh you, my people and our parents, you just have to please come to our rescue. We are suffering here, the aircraft has come to bombard us and killed many of us. Some are wounded. Every day we are in pain and suffering, so are our babies. Some of our husbands that we married also are injured, some dead. No one cares for us.
“Please go and beg the government of Nigeria to release the members of our abductors so that they too can free us to let us come home. We are really suffering, there is no food to eat, no good water to drink here.”
The north-east of Nigeria is in the grip of a polio crisis. Military helicopters have rushed vaccines to dangerous parts of the area, where Boko Haram operates and where two toddlers paralysed by the virus were recently discovered, health officials said.
The World Health Organisation said the wild virus has circulated undetected for years in the area where the Islamic extremists have prevented vaccinations.
Borno state health commissioner Ibrahim Miringa said recent attacks by the Islamic extremists prevented the emergency operation from getting health workers to two parts of Borno state where the children with polio were found.
Boko Haram has killed polio vaccinators in the past.
He said the two children, aged under two, were among refugees recently arrived from areas newly freed from Boko Haram.