Islamic State (IS) militants have claimed responsibility for an attack on an oil installation close to Libya's Ras Lanuf terminal.

An engineer at the port and an energy official allied with the country's eastern Government said at least two storage tanks from the Harouge Oil Operations company had been set on fire near Ras Lanuf, where militants also launched attacks earlier this month.

In a video released shortly after Thursday's attack, IS threatened to target even more of the nation's oil installations, taking advantage of a security vacuum to expand their presence in Libya.

"Today Es Sider port and Ras Lanuf, and tomorrow the port of Brega, and after the ports of Tobruk, Es Serir, Jallo, and al-Kufra," IS fighter Abu Abdelrahman al-Liby said in a video posted on the group's official Telegram channel.

Libya's oil industry has been hit by frequent attacks, strikes and protests as the country slipped into political turmoil after Moamar Gaddafi was overthrown in 2011.

Current production is under 400,000 barrels per day, less than a quarter of the 2011 high of 1.6 million.

An explosion south of the Ras Lanuf last week hit a major oil pipeline which runs from the Tibisti and Bayda fields, and had been closed for more than two years.

An oil official based in eastern Libya, Mohamed al-Manfi, said the blast was a result of sabotage.

In early January, IS attacked Ras Lanuf and the nearby terminal of Es Sider, killing at least 18 guards and setting fire to seven oil storage tanks.

Ras Lanuf and Es Sider, two of Libya's key export terminals, have been closed since December 2014. They lie between the city of Sirte, which is controlled by IS, and the eastern Libyan city of Benghazi.

Western powers are pushing Libya's factions to back a UN-brokered national unity government to join forces against IS, but the agreement faces major resistance from several factions on the ground.

Reuters