Libya's interim authorities say their fighters have entered the outskirts of the coastal city of Sirte, Muammar Gaddafi's birthplace and one of the last places still loyal to the fugitive leader.
The National Transitional Council says its fighters breached defences south and west of the city, about 8km from the centre, but met heavy resistance and retreated.
A council spokesperson says the fighters reportedly clashed with snipers in a high-rise tower and an elite unit of pro-Gaddafi troops.
Colonel Gaddafi's spokesperson, Moussa Ibrahim, told a Syrian television channel that "thousands of volunteers" were ready to "liberate Libya" from the NTC.
"We are in fact strong. We have the capabilities, the means and plans to liberate the whole of Libya," he said in a phone call to the pro-Gaddafi al-Rai channel.
NTC fighters are still facing resistance in the desert town of Bani Walid and the southern outpost of Sabha, as well as Sirte.
Meanwhile, Turkish PM Recep Tayyip Erdogan is in Libya as part of a tour asserting Ankara's regional influence and promoting democracy.
It comes a day after the leaders of Britain and France arrived in Libya, the first foreign leaders to visit since Colonel Gaddafi was ousted.
UK and France pledge continued NATO support
After talks in Tripoli with the National Transitional Council, UK Prime Minister David Cameron and French President Nicolas Sarkozy went to Benghazi where they were given a rousing reception by crowds in Freedom Square.
Mr Sarkozy plunged into the crowd, reaching across his bodyguards to shake the hands of waiting people, many of them waving French flags.
Earlier, Mr Cameron praised the NTC for the way it has established control over the country, but warned that the ''hardest part'' was still to come.
Both he and Mr Sarkozy said NATO would continue its mission under a UN mandate to protect Libyan civilians until the last remnants of pro-Gaddafi forces were defeated.
Britain and France were at the forefront of the NATO operation in Libya.
Mr Sarkozy urged Libyans to avoid ''vengeance and retaliation'', calling on them to preserve unity and seek reconciliation.