Islamic State-aligned jihadists have released five local aid workers abducted last month in violence-wracked northeastern Nigeria, security sources and one of those freed said Thursday.
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.
"We are all in good health. I and my colleagues are now at ALIMA office here in Maiduguri where we are staying for the night."
The negotiations for the release were initiated by the DSS, the security source said.
It was not clear whether ransom was paid for the aid workers' release.
A sister of Asabe Musa told AFP her sibling spoke with their mother on the phone from the DSS offices after her release.
"My sister was allowed to call our mother and confirm her release along with four others," Vicky Musa told AFP.
Asabe Musa was kidnapped along with two others on December 22 on their way to Maiduguri for Christmas from the garrison town of Monguno, 135 kilometres (84 miles) away.
On December 4 ISWAP claimed the abduction of two Red Cross staff along with 12 other passengers on a separate highway outside Maiduguri.
ISWAP has increasingly been abducting motorists at checkpoints in Borno state, targeting security personnel, anti-jihadist militia as well as Christians.
The United Nations Humanitarian coordinator in Nigeria, Edward Kallon, said he was "deeply relieved" at the news of the release.
But he said in a statement it was unfortunate that aid workers are being targeted by jihadists in Nigeria.
"These dedicated humanitarians were working to provide life-saving support to millions of Nigeria's most vulnerable in north-eastern Borno state...
"I also remain gravely concerned for the lives of our (Action Contre la Faim) colleague Grace Taku, abducted near Damasak in July 2019, and Alice Loksha, a nurse and a mother, abducted during an attack in Rann in March 2018. Both are still held captive by non-state armed groups".