Heavy fighting between local armed groups killed several people on the outskirts of Tripoli on Saturday, as interim government officials struggled to calm tensions amid talk of tribal feuds and diehard support for Muammar Gaddafi.
On a second day of clashes near a military camp lying among farms and villages between the capital and the port of Zawiyah, some 50 km (30 miles) to the west, anti-Gaddafi fighters from Zawiyah pounded targets with heavy machineguns, anti-aircraft cannon, rocket-propelled grenades and Grad rockets.
Incoming shellfire forced the Zawiyah fighters to take cover and retreat at times.
The fighting has fanned anxieties that, with tens of thousands of heavily armed men roaming a country still lacking new structures of government, frictions could escalate and hamper efforts to install democracy in place of Gaddafi's rule.
Zawiyah fighters, who said they had two men killed on Friday, put their own losses on Saturday at around 10, though there was considerable confusion at the scene. Senior figures who said they spoke for those on the other side, said they knew of no losses and blamed tension on misunderstandings.
Intense and prolonged exchanges of gunfire punctuated by explosions continued for several hours on Saturday afternoon, around a military base at Imaya, an area inhabited by people from the Wershifanna tribe, a big clan in the Tripoli region.
The area straddles the main highway connecting the capital to the Tunisian border and oil and gas facilities near Zawiyah.
Mohammed Sayeh, a member from the Wershifanna on the 51-seat National Transitional Council (NTC), Libya's interim rulers, played down the fighting, calling it an attack by men from Zawiyah who wanted control of the Imaya base and had been misled by a rumour that pro-Gaddafi fighters were in the area.
They have made propaganda that the Wershifanna are pro-Gaddafi to themselves an excuse to go through people's homes, take their cars, Sayeh told Reuters, adding that the NTC was working to calm the situation. These are false rumours.
Yet at the Zawiyah brigades' front line, field commander Walid bin Kora, speaking to Reuters as the sound of bullets and grenades filled the gathering dusk, insisted he and his men had seen organised fighting units with vehicles marked Brigade of the Martyr Muammar Gaddafi attack them and take prisoners.
He said Zawiyah fighters had seen tanks and green flags, a symbol of support for Gaddafi, and had captured mercenary pro-Gaddafi fighters from sub-Saharan Africa. It's a real army, bin Kora said of those he was facing as his brigade regrouped under a highway bridge.
There was no independent confirmation.
A paramedic from Zawiyah, who drove to the scene to help take troops back to Zawiyah hospital, said he knew of at least seven killed from their side.
Reuters journalists saw more than a dozen wounded fighters being evacuated from the area.
Fathi Ayad, an NTC military commander who is also from the Wershifanna, said the interim administration had brought together leaders from both sides and was confident a cease-fire would hold on Sunday. There was little sign of calm as darkness fell on Saturday.
Sayeh of the NTC said that NTC Chairman Mustafa Abdul Jalil had taken part in hours of talks through the night of Friday into Saturday to try to resolve the conflict. Sayeh said he was confident of a resolution: It's not a big deal, he said. They are young, they are excited, they heard these rumours.
This is not Sudan, it is not Iraq, it is not Afghanistan.
The incoming prime minister, Abdurrahim El-Keib, has promised to disarm militias and set up a national army, but has yet to announce a concrete timetable or form a government.
Abdul Jalil, who assured visiting EU foreign policy chief Catherine Ashton on Saturday that armed groups and weapons would be brought under control, said he expected Keib to have formed his government within a week.
It is not an issue of just saying 'OK, just give us your gun, go home', Keib told Reuters on Wednesday. We will look at the issues, evaluate and come up with programmes to take care of them and help them and make them feel important.
Abdel Hakim Belhadj, a prominent Islamist and head of the NTC's Military Council, told Reuters on Friday the fighting near Zawiyah was an isolated incident, a flare-up of an old feud.
(Additional reporting by Ayman al-Sahli in Imaya and Omar Younis, Labib Nasir, Alastair Macdonald and Taha Zargoun in Tripoli; Writing by Alastair Macdonald; editing by Tim Pearce)