Libyan oil production has fallen, turning back a hard-won increase since April in the revenue flow for the government facing increased fighting around the airport in the capital and in the eastern city of Benghazi.
The El-Feel oilfield last week was forced to cut back due to events in Tripoli, where two rival brigades of militias have fought over control of the airport.
El-Feel, operated by state-run National Oil Corporation and Italy's ENI, is protected by security guards from the northwestern Zintan region, whose fighters also protect the airport where clashes have gone on for a week.
National Oil Company spokesman Mohamed El Harari said output as of Monday was around 450,000 bpd compared with 555,000 bpd on Thursday.
At least 47 people have died in the week-long Tripoli airport clashes, which involved artillery, Grad rockets and anti-aircraft guns, in some of the heaviest street fighting since the 2011 civil war.
Fresh fighting broke out on Monday night in Tripoli and Benghazi where armed forces and troops loyal to a renegade former army general are battling Islamist militants who have set up base there.
There were no immediate reports on casualties from Monday's fighting in Benghazi or the Qasr Ben Ghashir neighborhood near Tripoli airport where residents have been forced from their homes or trapped by the gun battles.
“There are a lot of families still stuck and not able to get out because of the intensity of the shelling and bombing, which is with all kinds of heavy weapons,” said local area mayor Mohammad Abdullah.
The clashes have stopped most international flights, damaged more than a dozen planes parked at the airport - one Airbus jet billowed black smoke after being hit on Monday - and prompted the United Nations to pull its staff out of Libya.
The airport clash reflects national divisions between two main factions: those from the western town of Zintan and their allies who are loosely tied to the National Forces Alliance political movement, and the more Islamist-leaning Misrata brigades and allied militias who side with Justice and Construction Party, a wing of the Muslim Brotherhood.
Libya's oil resources have often been targeted by armed groups since 2011 to push the government for financial or political gain. Last year a string of protests slashed oil output to less than half the usual 1.4 million barrels per day.
A negotiated deal in April mostly ended a year-long blockade by a former rebel commander over four key oil ports, allowing Libya to slowly rebuild production, shipping crude and earning vital oil revenue.
One of Libya's ports, Brega, is expected to be operating within a “few days” after the government reached a deal with protesting security guards to end a blockade, NOC's Harari said.
According to Reuters AIS Live tanker tracking service, no tankers had loaded so far at Brega. One crude shipment left the 230,000 barrels-per-day Zawiya port, supplied by the El Sharara oilfield, which was recently reopened. The Olympic Spirit II, carrying Aframax, crude oil, headed to the Spanish port of Bilbao having left July 20.