Boko Haram has released a video apparently showing some of the schoolgirls kidnapped two years ago from the town of Chibok.
The footage, 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.
The kidnapping of the 276 girls triggered the global social media campaign #BringBackOurGirls, involving First lady Michelle Obama and a host of celebrities.
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 April 14, 2014, seizing the girls who had gone there to take exams.
Shortly afterwards the Islamist group released a video of the girls 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 recognized 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 organized by local officials in Maiduguri, capital of Borno state.
According to Amnesty International, about 2,000 children have been abducted by Boko Haram since 2014. Many are used as slaves, fighters and even suicide bombers.