Islamic State-aligned jihadists have released five local aid workers abducted last month in Borno State.
This was confirmed by the security sources and one of those freed.
The aid workers were seized along with other passengers in two separate incidents in December when fighters from Islamic State West Africa Province (ISWAP) disguised as soldiers intercepted vehicles on highways outside the Borno state capital of Maiduguri.
ISWAP, which split from the Boko Haram jihadist group in 2016, has focused on targeting military installations and troops since mid-2018.
However there has recently been an increase in attacks on civilians blamed on ISWAP.
The decade-long jihadist conflict in northeast Nigeria has killed 35,000 people and displaced around two million from their homes.
The violence has spread to neighbouring Niger, Chad and Cameroon, prompting the formation of a regional military coalition to fight the Islamists.
A security source told AFP “the five aid workers were released after days of mediated negotiations with ISWAP” on Wednesday.
The hostages are local staff of international humanitarian agencies, providing aid to thousands of people displaced by the violence in the region, the source said.
Asabe Musa, a hygiene specialist with ALIMA (Alliance for International Medical Action), a French NGO, is among the five freed hostages.
“We were released by our captors today (Wednesday). Two of us are from ALIMA, one each from Red Cross, Solidarity and IOM (International Office for Migration).
“We were first taken to the DSS headquarters before we were handed over to our various agencies,” she told AFP, referring to Nigeria’s domestic intelligence agency.