Mediaboss Marketing

Abdullah al-Thinni, who is recognised outside of Libya as the legitimate prime minister, retreated from the capital Tripoli and relocated his government into eastern Libya, after an Islamist-dominated group known as Libya Dawn seized Tripoli in August and set up its own administration.

In an attempt to minimise losses, Libya's National Oil Corporation invoked a contractual clause known as "force majeure", by which they were not forced to compensate their clients for the closure of Es Sider. They also called on the rival fighting factions to spare the country's energy infrastructure.

But for the rival governments, Libya's oil reserves are a key prize, not collateral damage.

On Saturday, Libya Dawn the newest of the Middle East's self-proclaimed revolutionary movements said it had launched an operation to "liberate oilfields and terminals".

Days earlier, Mr Thinni had said his government wanted to consolidate control over oil revenues by setting up a payment system which would bypass its political rivals in Tripoli.

Libya's oil reserves are among the biggest in the world, and production has repeatedly been affected by spasms of violence. Es Sider had only recently reopened after a one-year interruption which ended when rebels occupying the port struck a deal with the central government.

The question of who owns Libya's oil reserves is key to foreign buyers, most hailing from Europe and China.

Libya's energy industry had seen a modest recovery from a wave of protests until last month, when the southern El Sharara oilfield, one of Libya's largest, ceased production due to clashes and a pipeline closure.

More:
Libya's biggest oil exporting port closes as fighting intensifies