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.
Libya's oil production has recently been around 700,000 barrels per day (bpd), but has dropped to 663,000 bpd after Waha Oil Company cut output by about 35,000 bpd as a precaution due to the unrest, said Jadalla Alaokali, a board member of the National Oil Corporation (NOC).
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 NOC to end a long blockade in the area and more than double national output.
BDB leader Mustafa al-Sharksi told reporters that the group controlled about 170 km of coast stretching either side of the oil ports.
LNA spokesman Ahmed Mismari urged citizens in the region to restrict movement 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 mobilisation 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. Al-Sharksi said two BDB members had been killed and two wounded.
The BDB includes fighters who fled Benghazi as the LNA won ground there against Islamists and other opponents. They say they are trying to return to the city but want to secure the oil ports first.
Libya's oil production is 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.
A tanker that had been due to dock at Es Sider on Tuesday, 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 Thursday to load another cargo for OMV, the source said.
(Additional reporting by Ahmed Elumami in Tripoli, and by Ahmad Ghaddar and Julia Payne in London; Writing by Aidan Lewis; Editing by Julia Glover)