According to media reports, an air strike on the southern Libyan town of Murzuq has killed more than 30 people.
The Libyan National Army (LNA) confirmed a strike but denied they had targeted any civilians.
The LNA, led by Field Marshal Khalifa Haftar, began the second stage of its offensive on the Libyan capital Tripoli in July.
Tripoli, which is controlled by the Government of National Accord (GNA), has been under attack from the forces of Libyan National Army, commanded by Khalifa Haftar since April.
Libya has been engulfed in an armed conflict between opposing political forces since Western-backed militants murdered the country's former leader, Muammar Gaddafi, in 2011.