The Nigerian Islamist group Boko Haram has released a video purporting to show some of the kidnapped Chibok schoolgirls.
Some 50 girls wearing headscarves are seen behind a Boko Haram militant who demands the release of fighters in return for freeing the girls.
The militant also says some of the girls have been killed in air strikes.
The group seized 276 final-year girls from their school in the northern town of Chibok in April 2014.
Boko Haram is believed to still be holding more than 200 of those kidnapped.
The video begins with a shot of a masked man, carrying a gun, speaking to the camera. He says that some of the girls have been wounded and have life-threatening injuries, and that 40 have been "married".
"We don't want to do anything with these girls, our demand remains the same," he says in the Hausa language.
"We want the government to release our fighters who have been in detention for ages; otherwise, we will never release these girls."
The video concludes with footage of bodies, said to be the victims of air strikes, lying on the ground at another location.
The militant also carries out a staged interview with one of the captives, who calls herself Maida Yakubu, in which she is apparently used to convey the group's message to the government.
"What I can say is that our parents should take heart," she says. "Talk to the government so that we can be allowed to go home."
Maida's mother, Esther, is one of several parents of Chibok girls who recently published
open letters
to their daughters detailing the pain they feel at their children's absence and their hopes for the future.