They say they now control the city of Bin Jawad after clashes with rebels broke out on Monday.
Pro-Gadhafi fighters also say they have re-captured the rebel-held city of Zawiya, which is the closest to the capital Tripoli, but some residents reported that rebels still held the city's main square
At least 20 people were injured in Tuesday's clashes.
On a separate front in the east, Libyan warplanes launched at least five new airstrikes near rebel positions in the oil port of Ras Lanouf.
The one thing that seems to hold potential to tip the scales in the rebel's favor is international intervention. The U.S. says it has not ruled out using some type of military force.
The rebels are fighting to oust Gadhafi from power after more than 41 years, inspired by protesters who managed to topple authoritarian rulers in neighboring Tunisia and Egypt. However, the Libyan uprising has already proved much more violent.
The Associated Press contributed to this story.