Troops commanded by Libyan renegade general Khalifa Haftar have launched an offensive to seize back control of two of the country's key eastern oil terminals, according to a spokesman.
"Ground, sea and air forces launched joint attacks to liberate Ras Lanuf from terrorist groups," Khalifa al-Abidi said after orders were issued early on Tuesday for the push, which is also targeting the nearby Es Sider oil terminal.
Both sites were seized earlier this month by the Benghazi Defence Brigades (BDB) rival group.
At least nine people were killed in fighting on Friday as Haftar's eastern-based Libyan National Army (LNA) and allied forces retreated from the oil ports.
READ MORE: Benghazi Defence Brigades claim seizing Libyan cities
Al Jazeera's Mahmoud Abdelwahed, reporting from Tripoli, said that the BDB confirmed reports that their fighters had come under attack.
"The clashes have erupted again but the Benghazi Defence Brigades confirm that they have not lost Ras Lanuf yet to Haftar's forces."
The BDB are composed partly of fighters who were ousted from Benghazi by the LNA.
Libya splintered into rival political and armed groupings after the uprising that toppled Muammar Gaddafi in 2011. It remains deeply divided between factions based in the east and west that back rival governments and parliaments.
Haftar, who is aligned with the eastern parliament and government, has been fighting a two-year military campaign with his LNA forces against armed groups in Benghazi and elsewhere in the east.
Meanwhile, US and security sources on Tuesday told the Reuters news agency that Russia has deployed special forces and unmanned drones at Sidi Barrani, about 100km from the Egypt-Libya border, adding that any such Russian deployment might be part of an effort to support Haftar.
The reports were later denied by both Moscow and Cairo.
Back in January, Haftar was given a tour of a Russian aircraft carrier in the Mediterranean, according to Russian media reports, a show of Kremlin support for the faction leader who opposes Libya's UN-backed government.
Escalation of violence
The latest fighting around the terminals has raised the prospect of a new escalation of violence and put at risk a sharp boost to Libya's oil production achieved after the LNA took over four ports in September, ending a blockade at three of them.
Though Es Sider and Ras Lanuf have been reopened for exports, they were badly damaged in past fighting and are operating well below capacity.
It was not clear to what extent the BDB had gained control over the ports, or whether operations at the terminals had been affected.
READ MORE: Will losing oil ports end Haftar's power?
"Haftar claims to control most of the eastern part of Libya around Benghazi," Oliver Miles, former British ambassador to Libya, told Al Jazeera last week.
"But, control is a loose word. He's been fighting for a long time to deal with them and it has taken a long time time to clear them up. He's repeatedly said they've dealt with the problem but they keep reuniting."
Libya's oil production has recently been fluctuating around 700,000 barrels per day (bpd), more than double its output last year but still well under the 1.6 million bpd the OPEC member was producing before a 2011 uprising.
|Rival factions fight over key oil ports [Al Jazeera]
Source: Al Jazeera and news agencies