Libyan authorities have released Saadi Gaddafi, a son of the former leader Muammar Gaddafi who was ousted and killed during a 2011 uprising, a Libyan official source and a unity government source said on Sunday.

Saadi Gaddafi fled for Niger during the Nato-backed uprising, but was extradited to Libya in 2014 and has been imprisoned since then in Tripoli...