Story highlights

CNN exclusively obtained a "proof of life" video of kidnapped Nigerian schoolgirls

CNN team showed footage to mothers of the girls -- the first sign their daughters were alive

The footage prompts renewed anger at failure of authorities to rescue girls -- two years on

Abuja, Nigeria CNN  — 

It was footage that broke hearts around the world, underlining the ongoing suffering of the Chibok mothers – and the unimaginable plight faced by their daughters.

Images of Nigerian woman Rifkatu Ayuba overcome as she recognized her teen daughter, Saratu, in a “proof of life” video produced by her captors – and obtained exclusively by CNN – prompted renewed outrage over the 2014 kidnappings.

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From protesters marching in Nigerian cities to social media users in distant countries raising their voices, the story stirred fresh outpourings of anger and frustration.

Anger at the atrocity itself, but also at the official response. How was it that two years after Boko Haram kidnapped 276 girls from their school dormitory, the Nigerian government and the global community – which had expressed so resolutely its determination to #bringbackourgirls – had failed to rescue the 219 still missing?

And why had the Nigerian government – believed to have been in possession of the video since mid-January – failed to inform the families of the missing girls it had the film, the first glimmer of hope their daughters were still alive?

The video, obtained by CNN and showing 15 girls in robes identifying themselves, is believed to have been made in December in the course of negotiations between the government and parties claiming to represent Boko Haram.

Shot on Christmas Day, it was released by someone keen to give the girls’ parents hope that some of their daughters are still alive, and to motivate the government to help release them.

Two of the three women to whom CNN screened the footage were able to recognize their daughters, while a third was distressed it did not show her daughter. A classmate of the missing girls also identified several of the teens in the footage.

WATCH: CNN reporters take your questions on the stolen girls

Simple demand, difficult task

“Bring back our girls”: The demand, circulated on social media by ordinary citizens and such high-profile figures such as first lady Michelle Obama alike, is a simple one.

“We are the United States, all our resources, satellites, and badass attitude and we can’t help?” wrote Maryland-based Twitter user Derrick Gladden, in a comment that reflected widespread disillusionment that the international community had proved so impotent.

Britain’s government, for one, reiterated in a statement Thursday its commitment to help Nigeria defeat Boko Haram and rescue the girls, pointing to its boosted military, intelligence and development support since 2014.

But official Nigerian government responses to the video cast some light on the challenges faced in rescuing the girls, and betray an apparent degree of official confusion over the efforts.

Lai Mohammed, Nigeria’s minister of information, confirmed to CNN that the government has a copy of the “proof of life” video, and that it is in negotiations with the people who supplied it to try to secure the girls’ release.

“There are ongoing talks. We cannot ignore offers, we cannot ignore leads, but of course many of these investigations cannot be disclosed openly because they could also endanger the negotiations,” he said.

But he said he was unable to confirm or reject the authenticity of the footage, citing concerns that the girls did not appear to have changed appearance sufficiently, given that two years have elapsed since their disappearance.

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Borno governor: Military turning tide

Gov. Kashim Shettima, head of the northeastern Nigerian state of Borno from where the abducted girls hailed, told CNN he was not aware of the existence of the video and said as far as he knew, there were no ongoing negotiations.

He said that the government of former President Goodluck Jonathan – which had been criticized for its response to the kidnappings – had been in talks to release the girls but had been “deceived by some con artist – they even parted with some money.”

“As much as we are eager to secure their release we also need to be careful and vigilant who we interact with,” he said.

He remained confident the girls were alive and would be rescued, he said, pointing to major ongoing Nigerian military operations against Boko Haram in his state.

“Nine months ago, the prospects were very bleak. Maiduguri (Borno’s capital) was on the verge of falling into the hands of the insurgents,” he said. “Now practically all the local government areas in Borno have been liberated.”

Recent military successes effectively had eroded the territory held by the terror group, effectively limiting its footprint to the Sambisa Forest, a vast tract of dense vegetation in the southwestern part of Chad Basin National Park.

It has long been suspected that Sambisa Forest was the likely place where the girls were being held. But Shettima cautioned that a military operation to recover the girls would be highly risky, and carried the threat the girls would be killed in the effort.

“It’s a very delicate operation to rescue the girls. In an effort to engage in a commando-style operation, maybe the safety of the girls might be compromised,” he said.

First step: Find them

Retired Gen. Carter Ham, former head of U.S. Africa Command, agreed with that assessment, telling CNN any military rescue effort would be “an exceptionally complex operation.”

“The general consensus is that from the very start, the girls have probably been widely dispersed. That makes finding them very difficult,” he said.

Furthermore, he said, if a raid were made on one location where the girls were held, “would doing that present an increased risk to the others held elsewhere?”

The first step to bringing back the girls, he said, was to find them – a task that would rely on increased surveillance, signals interception and human intelligence within the region.

Nigeria’s military appeared to be making improvements – not long ago it faced issues with soldiers mutinying – but the rescue effort struggled to overcome a lackluster response in the crucial first days after the kidnappings.

“It does appear to me in hindsight from the early stages of the girls’ capture that perhaps not enough effort was focused on finding out where they might be,” Ham said.

“With each day that passes this problem becomes more and more complex.”

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Girls missing, not forgotten

But after two years since the abductions, the patience of families and the public is wearing thin.

“2 years and the entire world has failed to rescue the girls from those lunatics? Are we for real?” tweeted Moses Chikwanda from Lusaka, Zambia.

Former Nigerian Vice President Atiku Abubakar spoke for parents everywhere on contemplating the second anniversary of the girls’ disappearance.

“I have young daughters & I can only imagine the pain of forcibly separating them from me. I can only imagine the pains of the Chibok parents,” he tweeted.

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CNN’s Michael Holmes, Bryony Jones and Christina Zdanowicz contributed to this report.