Fighting between Gaddafi loyalists and rebel groups has been raging in the oil town of Brega.
There were also reports of clashes in nearby Ajdabiya Pro-government forces captured an oil installation in Brega but the rebels drove them out.
There are conflicting reports on the number of casualties.
Rebel fighters disputed the claims by Gaddafi loyalists that they advanced on Brega without using force.
“Around 100 cars carrying mercenaries arrived. They came to kill and they had heavy weapons such as rocket launchers and machine guns,” one eyewitness told euronews.
Over the past two weeks, Gaddafi’s regime has lost control over swathes of Libya’s territory.
The rebels have seized large parts of the east, although Gaddafi retains a tight grip on the capital, Tripoli.
His forces also hold the Libyan leader’s hometown of Sirte, as well as Gharyan and Sabratha in the country’s northwest.
The rebel National Libyan Council told the Reuters news agency its forces will push westwards if Gaddafi refuses to step down.