Reuters reports that armed clashes broke out at Waha Oil's Dahra oil field on Monday, when a militia attacked the security forces guarding it.
A source at the company said militia had fired at men working for the oil protection force guarding the field. He said the company was taking steps to move workers from the field for their security.
It was not immediately clear where the militia was from but the source said it was from around the coastal city of Sirte. The source said he believed the feud was over who would guard the facility.
Libya has set up a 15,000-strong special force, the Petroleum Facilities Guard (PFG), to secure its energy installations.
Earlier on Monday, Deputy Oil Minister Omar Shakmak said a protest at another field belonging to Waha, Gialo 59, had not disrupted output as demonstrators demanding local hiring of vehicles blocked its entrance for an eighth day.