Video posted on social video reportedly shows some of the 300 girls who were kidnapped more than two years ago.
Boko Haram has released a video of the Nigerian schoolgirls allegedly kidnapped two years ago, showing some who are still alive and claiming others died in air strikes.
The armed group, which has attacked both Muslims and Christians, seized 276 students from the Government Girls Secondary School in Chibok on the night of April 14, 2014. Fifty-seven managed to escape in the immediate aftermath.
"They should know that their children are still in our hands," says a man whose face was covered by a turban in the video posted on YouTube on Sunday, the AFP News agency reported.
Al Jazeera’s Ahmed Idris, reporting from Lagos, said the man in the video claimed to be the successor to Abubakar Shekau and called on the Nigerian government to release the groups’ fighters from prisons.
Earlier this month, ISIL named Abu Musab al-Barnawi as Boko Haram’s new leader, replacing Shekau, who’s seven-year rule killed more than 20,000 people and drove more than 2.2 millon from their homes.
"The speaker said military air strikes had killed many of the kidnapped Chibok schoolgirls, and he asked the parents of these girls to press the government to release the groups’ fighters from prisons across Nigeria," Idris said.
"The speaker also said that 40 of the schoolgirls were married, some were killed by airstrikes and there were several injuries.
He also used the video opportunity to assure his comrades in prison and urged them to be resilient and assured them they would be soon be freed," our correspondent added.
The kidnapping of the girls has become a political issue in Nigeria, with the government and military criticised for their handling of the incident and failure to track down the girls.
About 2,000 girls and boys have been abducted by Boko Haram since 2014, with many used as sex slaves, fighters and even suicide bombers, according to Amnesty International, the London-based human rights organisation.
The group has been waging a campaign against the Nigerian government for several years, battling what it calls Western influence.
In recent months, it has increasingly used suicide and bomb attacks as the Nigerian military pushes the group out of territories they once controlled.
President Muhammadu Buhari has declared Boko Haram "technically" defeated, and said success in the campaign would be measured on the return of the Chibok girls and other abductees.