Fighting late Sunday broke out between rival forces equipped with heavy weapons, with one group linked to the defense ministry and the other to the interior ministry, local media reported.
Libya’s ambulance service reported five dead, including a 10-year-old girl, and 13 injured in Zawiyah, some 40 kilometers (25 miles) west of the capital Tripoli.
The United Nations mission in Libya (UNSMIL) condemned the deadly clashes.
“The UN in Libya is greatly concerned about reports that civilians were injured and killed during armed clashes in Zawiyah,” it tweeted.
“We condemn the use of heavy artillery in densely populated neighborhoods.”
A security source, who requested anonymity, said the fighting broke out after a member of one group was killed by a supporter of the other in a dispute over fuel smuggling, which is common in this region bordering Tunisia.
The fighting comes amid a political crisis between backers of rival Libyan prime ministers Abdulhamid Dbeibah and Fathi Bashagha, whose administrations are vying for control of the oil-rich nation.
Dbeibah’s government was installed in Tripoli as part of a UN-led peace process last year, while Bashagha was appointed by Libya’s eastern-based parliament in February.
In late August, fighting between rival militias in Tripoli left 32 people dead and 159 injured.
Libya plunged into chaos following the 2011 overthrow and killing of dictator Moamer Kadhafi in a NATO-backed uprising, with myriad armed groups and foreign powers moving to fill the power vacuum.