Three fighters in a militia from Zawiyah, in western Libya, were killed in clashes with rival gunmen from another town, a local official said on Saturday.
Nureddin Nussi said the fighting on Friday pitted Zawiyah fighters against a militia from Wershefana, which lies between that town and Tripoli.
On Saturday, sporadic gunfire was heard in Al-Maya region, 27 kilometres (16 miles) west of the capital, AFP correspondents said.
Fighters from Zawiyah, 15 kilometres from Wershefana, had taken up positions on the coastal road, armed with Kalashknikov assault rifles, rocket-propelled grenades and anti-aircraft guns.
Nussi told AFP armed tribesmen from Wershefana had on Thursday set up checkpoints on the road to Zawiyah, blocking off access to residents and making about 15 arrests.
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Three Zawiyah fighters were killed when they intervened, he said.
Nussi said the Wershefana fighters were supporters of the ousted regime of Libya's slain leader Moamer Kadhafi and added that local leaders from Zawiyah had opened negotiations to avoid further bloodshed.
"It's a well-organised army which is trying to sow chaos," he said, adding that they used a tank and rocket fire on Saturday.
The official said armed men from Bani Walid, southeast of Tripoli and one of the last holdouts of pro-Kadhafi fighters before their defeat by rebels last month, were trying to join up with the Wershefana gunmen.
"We arrested two of them," he said.
But a member of the Wershefana group said the clashes were for control of a former barracks of Battalion 22, which was led by Kadhafi's son Khamis. "We've held it since the liberation. Now the Zawiyah rebels want to take it."
Tensions between former rebel groups which toppled the Kadhafi regime have raised fears of a new civil war, with Libya's transitional leaders setting the disarmament of militias and formation of a national army as key priorities.