By Ayman al-Warfalli
BENGHAZI, Libya (Reuters) - East Libyan forces carried out fresh air strikes on Monday and said they were mobilising 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 Friday 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.
LNA forces are currently stationed at Al Uqaylah, about 70 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 Monday, he said.
The LNA took over the ports of Es Sider, Ras Lanuf, Brega and Zueitina in September, allowing the National Oil Corporation (NOC) to end a long blockade in the area and more than double national output.
Al Uqaylah lies about 40km 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 mobilisiation of (LNA) forces to drive back the terrorist gangs in the Oil Crescent," he said in a statement.
Since clashes began on Friday, 18 of the LNA's forces have been killed and 15 wounded, a medical official in the nearby town of Ajdabiya said.
Libya's oil production has reached around 700,000 barrels per day (bpd) in recent weeks, more than double the OPEC member's output last year, but still far under the 1.6 million bpd 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.
The BDB are partly made up of fighters who fled Benghazi as the LNA made advances there in a three-year campaign to oust Islamists and other opponents from the city.
They say they are trying to return to Benghazi, 130km north of Zueitina.
(Writing by Aidan Lewis; Editing by Julia Glover)