Forces loyal to Libyan leader Moammar Gadhafi are reported to have pushed back rebels trying to advance west toward Gadhafi's hometown and stronghold of Sirte.
Foreign journalists said an onslaught Tuesday by the pro-Gadhafi fighters forced the rebels to retreat farther east.
On Monday, pro-government forces drove the rebels back with heavy tank and artillery fire.
International airstrikes against pro-Gadhafi troops have enabled the anti-government forces to recapture large amounts of territory in recent days. Among the areas taken back from pro-government forces were the eastern town of Bin Jawad and the key oil towns of Brega and Ras Lanuf.
The battle for Sirte is expected to be critical in the rebels' push to end Gadhafi's 42-year rule.
Sirte is dominated by members of the Libyan leader's Gadhadhfa tribe. But many in another large local tribem the Firjan, are believed to resent his rule, and rebels are hoping to encourage them and other tribes there to help them.
The Libyan capital, Tripoli, is another Gadhafi stronghold. Several powerful explosions were heard near the city late Monday.
Western nations began enforcing a United Nations-authorized no-fly zone over Libya on March 19. Allied warplanes targeted Sirte for the first time late Sunday.
On Monday, Qatar became the first Arab nation to recognize the rebels as having the sole legitimate right to lead Libya. Qatar is also participating with Western nations in imposing airstrikes on Libya. Kuwait's foreign minister also signaled that a formal recognition from his country was forthcoming.