The toll compiled from a security force loyal to Libya's UN-backed Government of National Accord (GNA) and the militia of the head of a former people smuggling network, Ahmad Dabbashi, could not be independently confirmed.
Dabbashi's militia said four of its fighters were killed and eight wounded, while a commander of the pro-GNA force, speaking on condition of anonymity, gave a casualty toll of two dead and 40 wounded among its ranks.
Libya has plunged into insecurity and political chaos since the ouster and killing of its longtime leader Moamer Kadhafi in a NATO-backed 2011 revolution.
People smugglers have fed on the turmoil, turning violence-wracked Libya into a key gateway for illegal migration to Europe.
Sabratha, 40 kilometres west of Tripoli, where the GNA is based, is Libya's main departure point for migrants trying to reach Europe.
Dabbashi is reportedly among several people smugglers who have decided to halt their lucrative business and cooperate with authorities.