Eastern Libyan forces loyal to commander Khalifa Haftar carried out four air strikes near the El Feel oilfield as a warning to a rival commander, a field engineer said on Saturday.
It was the first military action by the eastern army since it banned all flights in southern Libya without its authorisation on Friday.
The strikes were directed at commander Ali Kennah, who was inside the compound at the time, the engineer told Reuters. Kennah is allied to the internationally recognised Tripoli government, while Haftar backs a parallel administration in the east.
The fractured political climate has caused significant disruption to the country's oil industry.
The Tripoli Government of National Accord (GNA), backed by the United Nations, said in a statement that the strike targeted a civilian plane that was trying to evacuate a number of wounded people from the oilfield to Tripoli.
The strikes damaged the oilfield's infrastructure and its airport runway and "put civilian lives at risk", the statement added, without adding details of any casualties.
State oil firm NOC, which runs the El Feel field with foreign partners, could not be immediately reached for comment.
Haftar is a dominant figure in eastern Libya where his Libyan National Army group seized the second-largest city of Benghazi in 2017 by expelling militants.
Last month, his forces started an offensive in the south to fight militants and secure its oilfields, and on Wednesday made good on the promise by moving on the closed El Sharara field.
His forces have occupied a pumping station some 20 km (12 miles) from the main El Sharara field but not the rest of the 315,000 barrels a day site, according to a field engineer.
The El Feel field is located in the same southwestern region and is still producing crude, usually around 70,000 barrels a day.
El Sharara was shut in December after tribesmen and state guards seized it.
Kennah, the commander of the Sabha military zone who served under former dictator Muammar Gaddafi, was appointed by Prime Minister Fayez Seraj last week. Fayez leads the GNA.