Aircraft attacked a convoy carrying suspected Islamic State militants near the northwestern Libyan town of Bani Walid early on Sunday, an official said.
No group claimed responsibility for the attack, though both the United States and Libyan government forces have launched air strikes on jihadists in recent months.
Three huge explosions rocked the area around dawn, the member of Bani Walid's municipal council told Reuters.
People living in Ras al-Tbel, about 80 km south-east of Bani Walid, had seen the same convoy of up to 15 vehicles carrying the black flags of Islamic State over the past two days, the official added.
It was not immediately clear if the convoy was hit.
Jihadist groups have taken advantage of political chaos to expand their presence in Libya and fighters loyal to Islamic State have taken control of the coastal city of Sirte, about 260 km east of Bani Walid.
Western officials say they are discussing air strikes and special forces operations in Libya against the group that is seeking to set up a cross-border Islamic caliphate and has already seized large areas of Syria and neighbouring Iraq.
US aircraft attacked a suspected Islamic State training camp on the outskirts of the western Libyan city of Sabratha this month, and launched two more air strikes against jihadist commanders in Libya last year.