Rebel forces have routed most of Muammar Gaddafi's troops in the Libyan oil town of Brega in the biggest boost for the insurgents' military campaign in eastern Libya in weeks, a rebel spokesman said on Monday.
More than 30 people on both sides have been reported killed in fighting over the weekend.
The rebel fighters have encircled Brega, an oil export terminal with a refinery and chemical plant which for months marked the eastern limit of Gaddafi's control, rebel spokesman Shamsiddin Abdulmolah said.
But its streets are strewn with landmines, making it hard to secure full control of the area.
"The main body (of Gaddafi's forces) retreated to Ras Lanuf," which lies to the west, Abdulmolah said by telephone. "I am told they have some four-wheel-drive trucks with machineguns spread out between Ras Lanuf and Bishr."
Abdulmolah said 10 rebels were killed and 175 wounded on Saturday, and two were killed and 120 wounded on Sunday.
The bulk of the rebels' forces were now past Brega and were heading west towards the towns of Bishr and Ugayla, Abdulmolah said. "I am sure they will clash today or tomorrow in and around Bishr and Ugayla."
The official Libyan JANA news agency reported that 19 Gaddafi loyalists had died over the weekend as a result of NATO bombing in the Brega area.
While rebel fighters have been making gains in eastern and western Libya in recent days, Russia criticised the United States and other countries for recognising the rebel leadership as the legitimate government of Libya, saying they were taking sides in the insurgents' five-month-old war to oust Gaddafi.
"Those who declare recognition stand fully on the side of one political force in a civil war," Russian Foreign Minister Sergei Lavrov told reporters in Moscow on Monday.
U.S. Secretary of State Hillary Clinton announced U.S. recognition of the rebels on Friday, while in Turkey for a meeting of an international contact group on Libya -- a major diplomatic step that could unblock billions of dollars in frozen Libyan funds.
Russia and China have taken a softer line towards Gaddafi, and neither attended the contact group meeting.
Brega, about 750 km (465 miles) east of Tripoli, is the site of a strategic oil terminal. The attack could signal a new rebel push westwards from their main stronghold in the east of the country after weeks of stalemate.
Gaddafi is refusing to step down despite the five-month-old rebellion against his rule, a campaign of NATO air strikes, and the defections of members of his inner circle.
The slow progress of the rebel military campaign has caused strains within NATO, some member states pressing for a negotiated solution to hasten the end of a conflict many thought would last only a few weeks.
Reports have circulated that Gaddafi is seeking a negotiated way out of the crisis, but in a speech on Saturday he described the rebels as worthless traitors and rejected suggestions that he was about to leave the country.
Brega has changed hands several times in the back-and-forth fighting along Libya's Mediterranean coast since the rebellion began in February.
Rebels say taking it back will be a tipping point in the conflict on the eastern front.
NATO said it had on Monday struck an antenna radar system, which was being used for military purposes at Tripoli's main airport.
NATO warplanes have also been attacking pro-Gaddafi forces near Brega. The alliance said targets hit on Friday included one tank, five armoured fighting vehicles and two rocket launchers.
Libyan officials in Tripoli have made no comment on any fighting against the rebels in Brega, and it was not immediately possible to verify rebel accounts of what was happening there.
On another front, in the Western Mountains region southwest of Tripoli, pro-Gaddafi forces exchanged artillery fire on Sunday with rebels in the village of Al-Qawalish, a rebel fighter manning a checkpoint there told Reuters.
Despite resistance from Gaddafi troops, the rebels have made advances in the area.