A group of rebels have cut off a pipeline leading from the Zuwarah refinery near Khamassa to Tripoli, which is still controlled by Muammar Qaddafi.
Media reports say that about 20 rebels were involved in the attack, which cut of supply from the refinery.
The raid came as Nato continued its bombing campaign against the Qaddafi regime, last week hitting oil installations used to refuel the army.
Analysts believe that the air campaign alone will not force a resolution to the civil war, and that access to oil could become crucial.
“Any such developments will likely be influenced by outside factors such as Nato airstrikes, the regime feeling the squeeze of blockades and oil shortages, or the, at present unlikely, success of negotiations,” UK-based security analyst firm AKE wrote in a report.