Conditions set out by Boko Haram's leader for the release of the schoolgirls held hostage by the militants may lead to a deal that sees the girls freed, analysts said on Monday.
In a new video obtained by AFP, the group's leader Abubakar Shekau said the girls may be released once Nigeria frees all the Boko Haram prisoners it has in custody.
The government rejected that proposal and said it was not interested in any conditions dictated by the extremists who have killed thousands in a five-year uprising and claimed the shocking 14 April mass abduction in the northeastern town of Chibok, Borno state.
On the subject of talking to Boko Haram, Nigeria has sent contradictory messages in the past.
Months after claiming that dialogue with the militants was impossible, President Goodluck Jonathan last year tasked a high-level panel with negotiating a ceasefire, an offer ultimately rejected by Shekau.
Shehu Sani, an expert on Boko Haram and religious violence in northern Nigeria, wrote last week that the militants were likely to demand a prisoner release in exchange for teenage girls seized from their school in Chibok.
"A deal can be reached with the insurgents on this issue," Sani told AFP.
The military has been accused of rounding up thousands of Boko Haram suspects, including women and children, and holding them in atrocious conditions that have been criticised by rights groups.
Shekau has also made prisoner exchange demands before. An early example came in 2011, when Boko Haram wrote an open letter to the governor of northern Kano state, demanding the release of detainees.
Sani said Boko Haram detainees can be divided into three categories: senior insurgent commanders, foot soldiers and families members of Boko Haram leaders.
The government should release members of this third group "as a gesture", provided it was tied to the release of some of the Chibok hostages, Sani said.
Worth exploring
Elizabeth Donnelly, of the Africa Programme at the London-based think-tank Chatham House, agreed that a prisoner-for-hostage swap was "worth exploring".
"They need to take any opportunity they may have because this is about the lives of more than 200 children," she said.
Donnelly noted an important shift between Shekau's first video on the hostages, released on 5 May, where he boasted about the abduction, threatened to sell the girls as "slaves" and made no mention of their possible release.
While the threat to sell the girls was repeated on Monday, Shekau in the latest video also said that Boko Haram "will never release them [the girls] until after you release our brethren".
The floating of this condition may be a sign that Boko Haram was "reconsidering its position", Donnelly said. "There does seem to be a reappraisal."
Boko Haram's insurgency, which has so often targeted defenceless civilians, often appears totally "indiscriminate" but "there is an element of this group which is well-organised and thinks strategically", she added.
Outrage over the mass abductions has spread across the globe, with prominent personalities ranging from US First Lady Michelle Obama to Pope Francis calling for the girls immediate release.
Britain, China, France, the United States and Israel have all offered various levels of military and security cooperation to secure the girls' release.
Boko Haram's position may have been influenced by the offers of support from world powers, which is unprecedented in the five-year conflict.