The raid targeted "a meeting of terrorist leaders" in a house in the Ubari region, 1,000 kilometres south of the Libyan capital, Tripoli, said Sallak.
He later told AFP he was not immediately able to identify the jihadists targeted in the air strike.
The United State has carried out frequent raids on the Islamic State group in southern Libya.
Libya has been gripped by chaos since a NATO-backed uprising toppled and killed dictator Moamer Kadhafi in 2011, with rival administrations and multiple militias vying for control of the oil-rich country.
Jihadists and people-traffickers have taken advantage of the chaos to gain a foothold in the North African country.
IS seized Kadhafi's hometown of Sirte in June 2015 but were driven out of the coastal town in December the following year by pro-GNA forces with US air cover.
The jihadists are still active, however, in central and southern Libya.
Haftar supports an administration in the east of the country, opposed to the Tripoli-based government of Serraj, who has struggled to assert his authority across the country.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)