Libyan forces loyal to the eastern-based commander, General Khalifa Haftar, have been clashing in the south of the country with rebels from neighbouring Chad.
Gen Haftar’s self-styled Libyan National Army said it had carried out air strikes.
The rebels, from a group called the Front for Change and Concord in Chad, said their positions on the border between the two countries had been attacked.
It claimed French forces allied with Gen Haftar had been involved. France denies this.
Analysts say the fighting is another example of the instability of the Sahel region, where a range of armed groups operate across borders.