The United Nations voiced "horror" after reports that eight mass graves had been discovered in an area recently seized by the unity government after forces loyal to eastern strongman Khalifa Haftar withdrew.

Several presumed mass graves have been discovered near Tarhuna, southeast of the capital Tripoli, since it was seized back by forces loyal to the UN-recognised Government of National Accord on 5 June.

"We are searching all the mass graves to identify the bodies and return them to their families," said GNA interior minister Fathi Bachagha, who was in Tarhuna on Thursday.

Separately, 160 bodies were also discovered in the morgue by GNA forces upon their arrival in the city, according to the director of Tarhuna's public hospital, Aburawi al-Buzeidi.

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Tarhuna was the main rear base for a devastating year-long offensive by eastern-based Haftar's forces to seize the capital from the unity government.