The report found many cases of enforced disappearance, torture and rape of detainees in facilities maintained by the authorities or rival militias.

The people responsible for the abuses were not prosecuted but merely moved to other posts, according to the report.

The UN fact-finding mission says that repression and intimidation of activists, lawyers and journalists seems to have risen since presidential elections were postponed in December, putting UN-backed moves towards greater stability in renewed jeopardy.

Footage of a slave auction in Libya sparked global protests in 2017Image caption: Footage of a slave auction in Libya sparked global protests in 2017.