A new video released by Boko Haram appears to show some of the Chibok schoolgirls abducted two years ago.
The video, apparently filmed in December, was sent to the Nigerian government and shows 15 girls in black robes identifying themselves as pupils abducted from the school.
Some of those filmed have been identified by their parents. It is the first footage of the girls to be seen since May 2014.
Meanwhile, hundreds of parents are due to hold a march in the Nigerian capital, Abuja, to demand the government does more to find their daughters.
Boko Haram militants attacked the government boarding school in Borno state on 14 April 2014, seizing the girls who had gone there to take exams.Shortly afterwards they released a video of them and demanded a prisoner exchange.
Boko Haram’s leader, Abubakar Shekau, said the girls had converted to Islam and he threatened to force them into marriage with his fighters or sell them into slavery. As the months passed, about 57 students managed to escape but at least 219 are still missing.
The latest video, apparently filmed on Christmas Day 2015 and now broadcast on CNN, shows the girls pleading with the Nigerian government to co-operate with militants on their release. They said they were being treated well but wanted to be with their families.
Two mothers, Rifkatu Ayuba and Mary Ishaya, said they recognised their daughters in the video while a third mother, Yana Galang, identified five of the missing girls, Reuters reported.
They were shown the video at a screening organised by local officials in Maiduguri, capital of Borno state.
“They were definitely our daughters… all we want is for the government to bring back our girls,” said Mrs Galang.
Amnesty International says about 2,000 children have been abducted by Boko Haram since 2014. Many are used as sex slaves, fighters and even suicide bombers.
Although the militants are still launching attacks, the Nigerian army has made progress in its fight against them over the past year, our correspondent adds.
It has retaken towns and villages controlled by Boko Haram and has also freed hundreds of women and children held captive.