The fighting near Misrata lasted less than an hour, two residents of the area said. A fighter with another force that later moved in to stop the clashes said the two sides had stopped shooting, though there were also reports of fresh mobilisations in the area.
One of the two factions involved in Saturday's clashes is the Joint Operations Force linked to Abdulhamid al-Dbeibah, city residents said. The other is a local group that has not declared an affiliation in the political crisis.
The cause of the clashes near the junction of the main coastal highway leading to Tripoli was not immediately clear.
It was also not clear if there was any connection to the mobilization in recent days of Misrata-based forces aligned with the two main sides in a wider political standoff over control of the Libyan government.
Motorists trying to reach the main road towards Tripoli were turned back because of the security problems there, another city resident said.
Western Libya has been tense this year due to a political standoff between the government of al-Dbeibah in Tripoli, and a rival administration under Fathi Bashagha that was appointed by the parliament.