A militia opposed to Libyan strongman Khalifa Haftar on Thursday attacked oil sites under his control, a military source said, inflicting fresh disruption on an industry that forms the chaos-hit country's economic backbone.
The attack was carried out by the Benghazi Defence Brigades, including fighters driven from Benghazi city by forces loyal to Haftar, the source said.
Rival political authorities and militias have been vying for control of territory and Libya's oil wealth since the 2011 uprising that ousted and killed dictator Moamer Kadhafi.
The latest fighting took place south of Ras Lanuf and Al-Sidra, two terminals in eastern Libya severely damaged in clashes between the two groups in 2016 and 2017.
One of the reservoirs was hit by a rocket fired by the attackers and set ablaze, the military source said.
Libya's National Oil Company said in a statement it had evacuated staff "due to armed clashes in the area", with production falling around 240,000 barrels per day.
A spokesman for Haftar's self-styled Libyan National Army, which controls most of the country's east, said the attack had been repelled.
"The army and air force have been tracking down the Benghazi terrorist brigades," who fled the area, the spokesman said. It was not possible to independently verify this information.
"The attack aimed to reduce pressure on the terrorists in Derna," the LNA spokesman added.
The LNA launched an offensive on May 7 to "liberate" the coastal city of Derna, home to about 150,000 people and held by hardline Islamist fighters since the 2011.
"Haftar's forces are preoccupied with Derna, hence the timing", said Jalel Harchaoui, an associate and Libya expert at North Africa Risk Consulting.
Derna is the only major part of eastern Libya outside the LNA's control and is held by a coalition of jihadist militias, including groups close to Al-Qaeda.
Backed by the United Arab Emirates and Egypt, Haftar opposes an internationally recognised government based in Tripoli and supports a rival administration based in the east of the country.
In September 2016, Haftar's forces took control of Libya's four main oil terminals -- Zueitina, Brega, Ras Lanuf and Al-Sidra.
The terminals were for years blocked by the Petroleum Facilities Guard led by Ibrahim al-Jadhran, opposed to both Haftar and the internationally recognised government.
No oil was exported from these key terminals between the end of 2014 and their re-opening in 2016, costing Libya more than $130 billion (110 billion euros), according to NOC.
In March 2017, the Benghazi Defence Brigades seized control of Ras Lanuf and Al-Sidra terminals, only for the LNA to take them back days later.
Jadhran has kept a low profile since 2016, but appeared in a video on social media on Thursday, saying he had formed a coalition to take over the oil sites.
It was not possibly to verify immediately whether Jadhran was involved in Thursday's attack.
The arrival of a tanker to load crude at the Al-Sidra terminal has been postponed and NOC's board of directors is "following the situation closely," the oil firm said.
An oil refinery in Libya's northern town of Ras Lanuf on January 11, 2017