Libyan opposition forces say they have broken through government lines in the eastern oil port of Brega after days of fighting with troops loyal to leader Moammar Gadhafi.
Rebel commanders Monday said they have routed most of Mr. Gadhafi's troops, but that the city's streets are strewn with landmines, making it hard to secure full control.
More than 40 people on both sides have been killed in the fighting that began last week. Rebel medical sources reported 24 dead and scores wounded, but Libyan government spokesman Moussa Ibrahim said opposition fighters have lost many times more. He said loyalist troops have repelled the rebel advance.
The Los Angeles Times, quoting a doctor in opposition-held Ajdabiya, reported that more than half the rebel casualties were caused by hundreds of land mines laid by pro-Gadhafi forces.
The rebels control much of eastern Libya and parts of the west. They have been fighting since February to end Mr. Gadhafi's four decade-long autocratic rule. NATO warplanes have been helping the rebels by bombing pro-Gadhafi forces under a U.N. mandate to prevent government attacks on civilians.
NATO says it struck an antenna radar system at Tripoli's main airport Monday. It says the Libyan government was using the radar for military purposes.
The United States and its allies also have been trying to boost the rebels diplomatically, recognizing them as the legitimate authority of Libya at a conference in Istanbul last week.
Russian Foreign Minister Sergei Lavrov criticized that move on Monday, saying the 30 nations at the conference were picking one side in a civil war and trying to isolate the other. He said Moscow rejects a strategy of isolation as the solution to a political problem.
Lavrov also said Russia will not offer asylum to Mr. Gadhafi if he steps down, as the rebels and NATO are demanding. Mr. Gadhafi has vowed to remain in Libya and keep fighting until the end.
British Prime Minister David Cameron discussed the Libya conflict with South African President Jacob Zuma in Pretoria Monday. Mr. Cameron said he and Mr. Zuma agreed that a political transition in Libya must be led by the Libyan people, and result in the ultimate goal of a democratic nation without Mr. Gadhafi as its leader.
