East Libyan forces carried out fresh air strikes on March 6 and said they were mobilizing ground forces as they attempt to win back two of Libya's largest oil ports, military officials said.

Forces loyal to the eastern-based Libyan National Army (LNA) lost control of the ports of Sider and Ras Lanuf on March 3 to a rival faction known as the Benghazi Defence Brigades (BDB) and have been unable to dislodge them with air strikes and ground operations since then.

The escalation risks reversing a recent recovery in Libya's oil production and reigniting conflict between military factions based in eastern and western Libya that have been fighting on and off for the past three years.

Libya's oil production has recently been around 700,000 barrels per day (Mbbl/d), but has dropped to 663 Mbbl/d after Waha Oil Co. cut output by about 35 Mbbl/d as a precaution due to the unrest, said Jadalla Alaokali, a board member of National Oil Corp. (NOC).

LNA forces are currently stationed at Al Uqaylah, about 70 kilometers (km) (45 miles) southeast of Ras Lanuf, military spokesman Akram Buhaliqa said. LNA war planes conducted strikes near Ras Lanuf and Es Sider early on March 6, he said.

The LNA took over the ports of Es Sider, Ras Lanuf, Brega and Zueitina in September, allowing NOC to end a long blockade in the area and more than double national output.

Al Uqaylah lies about 40 km southwest of Brega, and about 120 km southwest of Zueitina, both still under LNA control.

LNA spokesman Ahmed Mismari urged citizens in the region to restrict their movements, and appealed to forces that captured Sirte, about 180 km east of Es Sider, from Islamic State last year, to stay within the coastal city to avoid being hit by air raids.

"There is a very large air and ground mobilization of [LNA] forces to drive back the terrorist gangs in the Oil Crescent," he said in a statement.

Since clashes began on March 3, 18 of the LNA's forces have been killed and 15 wounded, a medical official in the nearby town of Ajdabiya said.

OPEC member Libya's recent oil production is more than double its output last year, but still far under the 1.6 MMbbl/d it was producing before a 2011 uprising.

Es Sider and Ras Lanuf were badly damaged in previous rounds of fighting and have been operating far below normal capacity.

Waha Oil Co. pumps oil to Es Sider, but has reduced output "due the company's limited storage capacity and fears about the evolution of events in Es Sider," NOC official Alaokali said.

The number of workers at both Es Sider and Ras Lanuf has also been reduced.

A tanker that had been due to dock at Es Sider on March 7, the Amalthea, will instead go to Brega to load a cargo for Austria's OMV, a Libyan shipping source said. A second tanker, the Overseas Redwood, is due to dock at Es Sider on March 9 to load another cargo for OMV, the source said.