Islamist militants on Sunday killed five members of a force led by military strongman Khalifa Haftar in the country's east, a pro-Haftar news agency reported.
"Terrorist groups attacked at dawn Sunday three sites under the control" of Haftar's forces south of the eastern city of Derna, it said.
Four of Haftar's forces were also wounded, it added.
Derna was known for being a bastion for Islamist militants even before the 2011 uprising that toppled and killed longtime dictator Moamer Ghaddafi.
Haftar's forces are waging a campaign against Islamist militants groups, including efforts to capture the eastern city from the "Revolutionary Shura Council of Derna", a coalition of militias close to Al-Qaeda.
On Saturday, a pro-Haftar fighter group died as he took part in a mission to try and rescue a pilot whose plane had crashed in the same area.
The pilot who died in the crash, had been carrying out a raid against militants positions when his fighter jet was hit by a missile, the news agency said.
Haftar's forces have lost several aircraft in recent months.
The controversial strongman supports an administration based in the country's east that has refused to recognise the UN-backed Government of National Accord based in Tripoli.