Nigeria's former president Olusegun Obasanjo has met with people close to Boko Haram in an attempt to broker the release of more than 200 schoolgirls kidnapped by the armed group, a source close to the talks told the AFP news agency.
Reports of the talks emerged on Tuesday as Boko Haram was blamed for fresh attacks targeting the security forces, public buildings and a school in its northeastern stronghold.
The talks last weekend at Obasanjo's farm in southern Ogun state included relatives of senior Boko Haram fighters, intermediaries and the former president, the source said on condition of anonymity.
"The meeting was focused on how to free the girls through negotiation," said the source, referring to the kidnapped schoolgirls, whose abduction has triggered global outrage.
It was not clear if Obasanjo's weekend meeting had been sanctioned by the government.
RELATED: Limited choices for women in Nigeria's north
Obasanjo backed Jonathan's 2011 presidential campaign but the two are widely thought to have since fallen out.
According to the source, Obasanjo supported a prisoner-for-hostage swap that would see some of the girls released in exchange for a group of Boko Haram fighters held in Nigerian custody.
As a private citizen with damaged ties to the presidency, Obasanjo likely does not have the authority to negotiate any deal on the government's behalf, AFP reported
Abuja has officially ruled out a prisoner swap but sent intermediaries to meet Boko Haram in the northeast to negotiate for the girls' release.
On Monday evening, Nigeria's chief of defence staff, Air Chief Marshal Alex Badeh, said the 223 school girls still missing had been located but cast doubt on the prospect of any rescue by force.
The United States however expressed scepticism that the girls had even been located by Nigeria, stating that it had no "independent information" on the matter.
US State Department Spokeswoman Jen Psaki told journalists in Washington that "for the girls' safety and wellbeing, we certainly would not discuss publicly" having found them, even if the reports were true.
Washington has deployed surveillance drones, spy planes and about 30 civilian and military specialists to support Nigeria's security forces in the search.
Meanwhile, Cameroon said it had begun deploying 3,000 extra troops to buttress its border with Nigeria against the threat posed by marauding militants.
Nigeria's response to the mass abduction has been widely criticised and the hostage crisis has brought unprecedented international attention to Boko Haram's five-year extremist uprising.