The family of the Union of Oil Workers' head, Saad Al-Fakhri, confirmed his release on Friday, after more than a month of detention under the eastern authorities prison.

"I assure you that this is only a routine investigation and interrogation that required a precautionary measure from one of the security services," Al-Fakhri said in a brief statement on Facebook, following his release.

Gunmen kidnapped Al-Fakhri near his home in the town of Suluq town, about 50 km south of Benghazi on April 29 last, where he was taken to an unknown destination.