Libya's oil output has fallen to 620,000 barrels per day (Mbbl/d), a drop of about 80 Mbbl/d since clashes erupted around some of the country's major export terminals, the head of the National Oil Corp. (NOC) said on March 9.

Mustafa Sanalla told Reuters that production by Waha Oil Co., a joint venture (JV) between NOC and foreign partners, had been entirely halted. Waha pumps oil to Es Sider, one of two ports that the eastern-based Libyan National Army (LNA) lost control of to a rival faction on March 3.

A port official at Ras Lanuf, a neighboring terminal that the LNA also withdrew from, said that production by another NOC JV, Harouge Oil Operations, had also been affected, without giving details.

Libyan oil officials said staff at Es Sider and Ras Lanuf have been reduced to a minimum since a faction known as the Benghazi Defence Brigades (BDB) seized them in clashes, and that the area is effectively a military zone.

The BDB said they have handed the ports over to a Petroleum Facilities Guard (PFG) force sanctioned by the UN-backed government in Tripoli, and that they would allow oil to flow.

However, the clashes are a new challenge to Libyan efforts to boost output, which had more than doubled since the LNA took over the Oil Crescent ports in September and ended a long blockade.

Es Sider and Ras Lanuf have a potential joint capacity of 600 Mbbl/d, but had been exporting a fraction of that partly due to damage in previous violence.

National production earlier during the week of March 6 had been relatively stable at about 670 Mbbl/d.

Brega and Zueitina, two other ports on the stretch of coastline southwest of Benghazi known as the Oil Crescent, remain under LNA control.

Waha Oil Co. is a JV between the NOC, Marathon Oil Corp. (NYSE: MRO), Hess Corp. (NYSE: HES) and ConocoPhillips (NYSE: COP). Harouge is a JV between the NOC and Canada's Suncor.