Lagos (AFP) - Nigeria's government on Thursday said it was studying a "proof of life" video showing 15 of the more than 200 schoolgirls abducted by Boko Haram, as parents and their supporters marked the second anniversary of the kidnapping.
The footage is the first time any of the missing girls have been seen since a previous Boko Haram video in May 2014, when about 100 were seen in Islamic dress reciting the Koran.
A total of 276 girls were abducted from the Government Girls Secondary School in Chibok, northeast Nigeria, on April 14, 2014. Fifty-seven escaped in the immediate aftermath.
Three mothers and a classmate of the 219 schoolgirls still missing confirmed the identities of the girls in the images first broadcast on CNN on Wednesday night.
Borno state governor Kashim Shettima, on a visit to Chibok, where parents of the missing girls held a vigil and said prayers at the school site, said: "The video... is of the Chibok girls. It's good news."
A senior government source told AFP it had received the video, which shows the girls in black hijabs, stating their names, that they were abducted from Chibok and saying they were "all well".
The video was said to have been shot on December 25 last year.
But the source said they were keen to avoid the problems encountered by the previous administration, which prematurely announced talks with Boko Haram elements and even a ceasefire.
"Our intelligence and security authorities... received a similar video in July last year and when they followed the lead it led to a cul-de sac," he revealed.
Contact could not be made and it was impossible to determine the identities of the purported Boko Haram members who sent it or if the move had the blessing of the group's leadership, he added.
- Factionalised -
Boko Haram has long been known to be factionalised, comprising groups of ideologically sympathetic fighters who do not always act under the direct orders of senior commanders.
In an indication the latest video and the previous unpublicised message may have come from one of these factions, the source also said the government had received a ransom demand last July.
The group asked for one million euros ($1.1 million) for 10 of the girls, the source disclosed.
That lends weight to theories the Chibok girls were split up following the abduction and were being held separately in different locations, complicating any possible talks or rescue bid.
AFP has also seen photographs of five girls that were sent to the government in mid-January this year as part of the same bid for negotiations.
Boko Haram's leader Abubakar Shekau has previously said the girls would be released in exchange for Islamist fighters held in Nigerian custody.
- Prayers, vigils -
Thursday's two-year anniversary was marked across Nigeria with vigils and protest marches, including at the site of the abduction involving many of the missing girls' parents, wearing black.
Yakubu Nkeki, head of the Abducted Chibok Girls Parents' group, read a letter to the teenagers, praying for them to be kept "safe and sound, wherever you are and the condition you find yourselves".
Governor Shettima promised the girls' swift return. "We are doing all we can to make sure these girls are found," he said.
In the commercial hub, Lagos, and in the capital, Abuja, hundreds of protesters from the #BringBackOurGirls movement gathered to renewed calls for the release of the girls and other victims.
Boko Haram has used kidnapping as a weapon, seizing thousands of women and young girls, and forcibly conscripting men and boys, in a conflict that has killed an estimated 20,000 since 2009.
The men and boys have been forced to fight in Boko Haram's ranks, while the girls and women have been turned into sex slaves and, increasingly, suicide bombers.
Amnesty International called for the release of all captives and said the Chibok girls symbolised "all the civilians whose lives have been devastated by Boko Haram".
President Muhammadu Buhari, currently on a visit to China, has said Boko Haram has been "technically" defeated but success would be measured on the return of the Chibok girls and other abductees.
The International Crisis Group said the anniversary was an opportunity to address the conflict's effect on children as the military frees more areas from Boko Haram's control.
Human Rights Watch said this week some 952,000 of the 2.6 million people displaced by the violence were children, who had been "robbed" of their right to education by attacks on schools.