Nigerian Islamist group Boko Haram has released a video apparently showing recent footage of schoolgirls they abducted from the northern town of Chibok.
Some 50 girls are shown with a gunman who demands the release of fighters in return for the girls, and says some girls died in air strikes.
The government says it is in touch with the militants behind the video.
The group is said to be holding more than 200 of the 276 girls it seized from a school in April 2014.
Non-Muslims were forcibly converted to Islam, and it is feared that many of the schoolgirls have been sexually abused and forced into "marriage" by their captors.
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 want to send this message first to the parents of these girls for them to know that these girls are still with us, some of them, and secondly they should tell the Federal Government of Nigeria, to with immediate effect, release our imprisoned brothers," the man said.
"Some of the girls, about forty of them with God's permission have been married, some of them have died as a result of bombing by the infidels," he said.
Speaking in the Hausa language, the gunman says the girls on display will "never" be returned if the government does not release Boko Haram fighters who have been "in detention for ages".
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 asks parents to appeal to the government.
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.
Another girl among those standing in the background can be seen with a baby. Some of the girls can be seen weeping as Maida speaks.
A leading member of the Bring Back Our Girls movement which campaigns for their release said after watching the video that she was terrified by what she had seen. "Everybody should be disturbed by the conditions of the girls," Aisha Yesufu said.
Boko Haram has waged a violent campaign for years in northern Nigeria in its quest for Islamic rule, and a faction of the group recently pledged loyalty to so-called Islamic State, the militant group which controls parts of northern Syria and Iraq.
Thousands of people have been killed or captured by Boko Haram, whose name translates as "Western education is forbidden".
Many of the girls abducted in Chibok were Christian.
- BBC / Reuters